App puchases - Credit Limit Renew

So I guess every T-Mobile customer has a $80 credit limit they will give you to charge in app purchases and such, like on Google play. I used mine up in July but the charges don't come until September I was told, which was correct I paid my usual amount for Bill this month. Now it's a new billing cycle period on Aug. 28 and I should have my credit able to charge up to a new $80. But so far it's not letting me ???  I'm confused, because this is a new billing cycle correct??  Last billing cycle went  to Aug. 27, now it's 28th And there is no reset on mine. When I called yesterday on 27th,.she said today the 28th I should have a new line of $80 credit able.