I had the same issue with my account being suspended this past Friday. Here is what happened, and hopefully this information is helpful to anybody that is having this experience.
This issue had never happened to me before. I was unable to make or receive phone calls, send or receive text messages, or use phone data (even my add-ons). All incoming calls would go to voicemail (I don't know if I had any voicemail messages to confirm that the system would store my messages). I had people send me text messages during the day but they never came through once my account was re-activated. Fortunately I had access to another phone and internet aside from my phone to check into the issue. The self-serve indicated that my account was suspended but not to worry if I had auto-pay enabled. I attempted to manually make a payment through the self-service with my card on file, which did not work. I also wasn't able to update my credit card information on the self-serve (my card is not expired). I tried using *611 to make a payment with my credit card on file, which the automated system told me to contact my credit card company. My credit card company reported that there were no declined transactions or issues with my credit card. I suspected that there was a problem with the payment system. I went to Wal-Mart to purchase a voucher, applied it, and everything was up and running immediately.
For anybody that does not have access to another phone or internet aside from their phone, this is a bit of a concern, and it is worth heeding the advice of @Staliger to have a voucher on hand for any system hiccups. Google indicates that there are online sources to purchase vouchers, which are available at an additional cost.
