Struggling for two years to cancel debit orders permanently

I have been trying to get some of my Old Mutual insurances cancelled with no success as they keep being debited and only receive back some of the money debited, which also affects my bank account. My first attemp was in December 2022 and then the whole of 2023 as well. I am a pensioner and need all the money I can spair, thus me cancelling these 5 insurances. I need all the money that has been short paid since 2022 to be returned to my account, as well as the debit orders to cancelled permanently. Two years of struggling to do something simple is very disappointing from a highly respected company.