This sort of thing is the reason for the 10-day advance notice of varying amounts requirement in section 205.10. The cell phone company has to bill the customer at least 10 days before issuing the debit. Of course, we all know that bills like this take a few days to arrive, even if they are presented online. So that 10 day period make effectively be shorter.
If the customer notified the cellular carrier not to make the debit before the EFT was entered, notice is effective under both Reg. E and NACHA rules. The company should not enter the debit. If it does, your customer has the right to recovery from you for paying an unauthorized transaction. You have the right to recover from the phone company via the ACH if your customer provides a timely WSUPP.
If the customer notifies you of the revocation of the authorization before the debit posts, you have to put something up on your system to stop it and send it back.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8