Telcel Amigo is a prepaid phone account in Mexico. If you don't add money to it for a while, you can lose the balance on it, and eventually your number. To avoid this, you should add some money ("minutes", if you're used to a US phone), at least once every two months. You can do this at a store in Mexico, or with a scratch card, or online at various sites described below.
In Mexico
If you're in Mexico, the easiest way to add money is to go to an Oxxo store, give them the money, and the phone number. If you add under 100 pesos, the validity of the balance is short (one month or less), so it's always best to add 100 pesos or more. This will increase the expiry date of your entire balance by 60 days. You will get a message on your phone showing it has been added.
You can also buy scratch cards, again it's best to get at least 100 pesos. These cards have instructions on the back. They are getting harder to find, now that more stores like Oxxo have instant recharges.
If you recharge with 200 pesos or more, you get an additional "gift" regalo balance. This is of dubious benefit, as that can only be used for Telcel-to-Telcel calls (and a few other less useful things). Still, it's free, doesn't do any harm. But if you're a low user, 100 pesos each two months is enough.
Many stores other than Oxxo offer the recharges, some smaller stores may add a small service fee.
Online - third party sites
I've used Babblebug several times to add money to a Telcel phone (click on the "international cellular" section then choose Mexico). They do both Telcel and Movistar recharges.
The phone doesn't need to be in Mexico. When I used it, it was $10 (looks like it's $10.99 now), this adds 100 pesos (or more?) to the account and 2 months to the validity of the entire balance. The amount is added almost instantly.
There are other companies like ezetop (who say they add 135 pesos for 10 dollars), but Babblebug is the one I have experience with.
Online - Telcel customer portal
First, you need to register your phone on the Telcel customer portal. This only needs to be done once.
You can then, amongst other things, add money to your phone from a credit card (including with credit cards issued in the USA and other countries). Note that the transaction is within Mexico, so a US or other foreign credit card will probably add an international transaction fee of around 3%, or maybe block the transaction entirely unless you tell them in advance the card will be used in Mexico.
So, if that's OK, to pay with a credit card, first sign on to your account on the portal.
Click onTiempo Aire con Cargo a Tarjeta (add airtime from credit card) under servicios on the right column:
Initial tab is Recarga de una Vez (recharge one time). The other options are to set up scheduled recharges, and an admin page.
Choose your phone number (or another number you want to add money to), the Monto (amount) - 100 pesos for example - and Nueva Tarjeta (new card). More fields will now appear, for you to enter the credit card and address details.
Enter the Tipo - Type - select Visa or Mastercard (can't use Amex or Discover); the Nuevo Número de Tarjeta - number of new card (16 digits); Fecha de Vencimiento - expiry date; and Código de Seguridad - CVC security code (last three digits on signature strip).
For Nombre del Titular enter the cardholder name: last name in Nombre, first name in Apellido(s).
Now enter the billing address of the card: País - country (Estados Unidos for USA); Ciudad - city; Estado - state; Dirección - street address (no commas or symbols); Delegación o Municipio - suburb (or just re-enter city name); Código Postal - zip code.
If you've entered a new phone number you will see: ¿Deseas guardar el número de Teléfono para futuras recargas? - Save this phone number to recharge another time? - select yes or no.
Otherwise, the next question is: ¿Deseas guardar los datos de tu Tarjeta para pagos posteriores? - save credit card data to pay another time? - select yes or no.
Click on Siguente (next).
Next page shows the data you entered, and a box down the end next to: He leído y estoy de acuerdo con los Términos y Condiciones de Compra de Tiempo Aire con Cargo a Tarjeta a través de Internet. Click on that box to say you agree with the terms and conditions, then Siguente (next).
Next page should show that it's worked, if your credit card company accepted it. You should also receive a text message on your phone a few seconds later to confirm it.
Click on Consulta tu Saldo (under Mi Cuenta in right column of the Telcel customer page) to see your new balances and the new expiry date.
The transaction will appear on your credit card as "Vesta Mi Telcel Com Mexico Mex" (Vesta is the processing company Telcel uses).
Mexican Bank Accounts
You can add money to your Telcel phone with the online banking of some Mexican bank accounts, for example a Bancomer Peso account. Again neither the phone nor you have to be in Mexico.
On Bancomer, it's the Compra Tiempo Aire section when logged onto online banking. If I remember right, you first have to register the phone (once), then you can add money to it in the future. Note that any money sent to phones from your Bancomer account comes out of your daily ATM cash limit. For example if your ATM limit is 3000 pesos and you send 500 pesos to your phone, you can only draw out 2500 pesos cash for the rest of that day.
Some ATM machines (in Mexico) have an option to send money to your phone, from your Mexican bank account.
Gift
It's possible to send a balance from one card to another as a gift. However, the balance when it arrives is just "regalo" balance, can only be used for Telcel-to-Telcel calls (and a few other things). I don't recommend this.
When to recharge
You can check the balance and expiry of your phone by entering *133# (then send/green). Don't do this too often, it costs 0.85 pesos each time (more if you are in the US). Remember the expiry date is shown day/month/year, You can also check it from the Telcel customer website for free, after you have registered.
You should recharge before it expires (at least few days before is best). Then, any existing balances roll over. If you leave it until after it expires, the previous balances are lost, but you should keep your number (not balance) if you then recharge within the next 3-6 months.
