Gas company not honoring the credit a technician told me I'd get to my account for their mistake, is there anything I can do?

After a 2 month investigation into an unusually high gas bill in July, the company sent out a 2nd technician to my apartment to investigate further. The technician told me there had been a mistake on their part and if I paid the bill, the amount would be credited to my account with future bills deducted from the amount. When I got the next month's bill there was no deduction so I called the company. They told me they cannot honor what the technician said because there were no notes. They told me there was nothing wrong, and the technician shouldn't have told me to do that. Is there anything I can do about this?