Debid orderr higher than agreed premium, poor customer service....they keep saying they will sort it out and they don't!

I signed up for motor warranty Plan 2 in September, and they confirmed the prices on the phone. This was in September 2023. However, when debit order went out, the amount was for Plan 1. I informed them of this and have been following up. It is now May 2024, nothing has been done. I'm about to take them to Ombud as I speak.