Tracker not taking responsibility for wrong doing

I upgraded my month to month contract to a 3yrs contract with traker on 18May2023. Come the time for debit order, tracker debited extra 170% on my account. On 7June I contacted customer service o resolve the matter and the following day I got a letter advicing me of a refund which amounted to 44%. A week later I did another follow up and was also told that the remainder of extra charge will be refunded. A week went by and there was no refund as promised. On June 26 I send the letter to the credit manager who was handling my account. I got a response the following day saying the part of remaining funds were offset from my next monthly subscription while initialy they commited to a refund.