Do you mean you were not able to cancel an automatic charge arrangement -or- do you mean you were unable to dispute a specific charge from a series preauthorized series?
I was not able to cancel. It was not a dispute over previous charges, but a desire to not allow future charges. Was told by AMEX they could not stop the upcoming charges. I mentioned then the only way to get out of the autocharge was to close my account and would consider that option. Centurion application showed up the next week or so. Hardly an olive branch, give us $7500 and we can make nice.
You can call each month and pay your bill, that way the merchant has to negotiate in good faith if there is an issue, knowing payment is conditional on them fixing the problem for you.