On the 18th of August an amount was deducted for an online purchase which to my knowledge I didn't do

On the 18th of August an amount was deducted for an online purchase which to my knowledge I didn't do. I contacted FNB and was asked to fill in a dispute form. Which I did. I did not receive any reply from the bank so I called them. I was advised it takes 40 working days. After the 40 daya I received an email stating that I should contact the ***** department. I called again and I asked to speak to a Manager. I was told the manager will contact me. To date the manager is still not available. Could FNB not contact me and inform what the issue to is. Service at this bank is pathetic. May be I should move over to another bank. Thank u