Cant Access prepaid account

Hello,

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Lately i ported my phone number to at&t, i have tried to create a AT&T prepaid account so i will be able to manage things like payments in the future, but whenever it asks me for my 10 digit phone number....i enter it and all it says is Error, the information is not valid, at first i assumed maybe i just put in the wrong password, so i went to forgot password, so i put in my 10 digit phone number in order to send an online pin, but once again it said the information i put in was not valid. My number was successfully ported over so there should not be an issue...how can this be resolved?!!