Appalling and *****ulent service

I was using rain 4g( sim only) for more than 3 years, last year I decided to upgrade to the 5g which comes with the rooter. Rain delivered the rooter and the according to my knowledge, an upgrade means the previous 4g sim no longer works. From the very first month, rain debited my account for both contracts. I called and I was advised it was an error and whoever was responsible for cancelling the 4g didn’t. That was 4-5 months ago…. Rain has been double debiting my account and everytime I call in they promise the issue has been escalated and should be resolved in a few days. I have wasted a lot of time, energy and money also because I’m the one who’s paying for all the calls. I want all my money back and rain can even collect their router as I’m sick of their terrible customer service.