Cancellations not processed and I’m still being charged

I have been trying for months to cancel some small contracts. At the stores I keep getting told I have to phone cancellations. I have phone cancellations 3 times. Each time I am assured that the cancellation is processed and will be effective from the end of the month. It is now 4 months later and I am still being charged for some contracts that I don’t need and thought were cancelled.