My Mom still pays by check as soon as her bill is received and her copy shows that ATT ran the payme

My Mom still pays by check as soon as her bill is received and her copy shows that ATT ran her payment for 2 cents less than the amount of the check.  The check was written for the correct amount but she was charged $9 for their mistake. She has a copy of the check and the statement proving their error but if this were on a large scale, it could very possibly lead ATT to receive huge amounts of money for penalties charged to consumers who didn't bother to follow up on the error(s).  She called and was told it was short 2 cents but her check proves otherwise. Someone needs to put some safeguards in the system - banks used to have somethng called a "plug pocket" for small "discrepancies". She spoke with a rep who removed the fee but now he's given her a figure for the current month that doesn't make sense.  She's calling them again tomorrow to get the breakdown of the new amount.  She does not trust auto pay and does not own a computer. and....we have been lifetime customers of ATT.