How much do customers have to pay for inefficiency at FNB.

HELP!!!! For years now, FNB has been overcharging me on my credit card. In addition, they have been overcharging me on my cell phone account. I have been trying for 2 months to get FNB to deal with both these issues - No luck - It is so frustrating, I was told that they would refund me for 3 months back on the overcharge (even though they have been overcharging me for more like three years) but since then another charge went off on my card at the higher rate and now I bet they will not refund me for four months because they have a policy I am told. After being on the phone today for 50 minutes, the agent then had the audacity to cut me off when I asked to speak to the manager who he said he had reported the matter to. Should I assume he was lying in the first place and that my case had not indeed been escalated? The thought of going through this whole scenario for the fourth time is daunting.