AT&T Prepaid Sign-in

Hi, I've been using AT&T Prepaid plan ($35/mo) but I had to travel overseas since late April.

I had forgotten to switch to the 25cent/min plan (to keep my number activated) but when I tried to sign-in in early May, the page kept giving me an error.

I'm still unable to sign-in to my account, and I'm afraid that my number might have been deactivated and that I might not be able to use it once I re-enter next month.

What's the maximum number of days that Prepaid numbers stay activated for? And is there something I can do while I'm overseas to solve this sign-in error issue?