Correct me if I am wrong

I asked for a refund from the stupid host AIT which gave me a cancellation number. I told the bank to cancel the payment of around $300 but the bank insisted on a written letter about the payment dispute which finally I sent them along with the cancellation mail from AIT Inc.

After 3 weeks, the bank, whose customer support section is run by a well-known two-letter company, tells me that it didn't receive any mail. It ticked me off for I have the proof of the courier bill and on top of it, they asked to check my memory whether I really sent one. This time it pissed me so badly I told them I'm going to send an email to two-lettered company's corporate people about the dismal performance of the customer service department. Finally things were sorted.

The issue is not that. This was the outcome: My mother who noticed my anger and the usage of words calls me a person with severe attitude problem. Excuse me? Was my behaviour right or wrong with the bank's support employees? Please opine freely so that I can get a good night's sleep.