Depending on the type of phone you have, you can top it up online with a credit card or by paying a third party to load a designated amount of money and corresponding minutes for you onto your phone. You also can enter the PIN from a prepaid phone card.
Singtel is an example of a prepaid phone product that you can top up online. Log into your account at Singtel.com. Click Top Up Now, enter the phone number to top up, select an amount, a payment method and enter any credit card or gift card information if applicable.
If you have a simple pay-as-go phone without Internet access, third-party vendors like Western Union offer reload options for topping up your phone. Fill out a special reload form at a Western Union location, and then give the completed form, reload amount and any associated fees to the agent. Your minutes are available very soon after the agent processes your request.
You can buy prepaid cards at gas stations and large stores, such as Walmart. In its brick-and-mortar stores and at Walmart.com, where you can purchase e-cards, there are various denominations for such brands as Straight Talk, TracFone and AT&T Go Phone.
To top up a prepaid phone with a phone card, purchase the desired amount and follow the related instructions. Every phone is different, but you typically have to dial a phone number, follow some prompts, and then enter a PIN.