I have signed up with Rain on their 5g internet, their internet is working well so far but I have a query with their billing, it seems they over billed me in February

I have signed up with Rain on their 5g internet, their internet is working well so far but I have a query with their billing, it seems they over billed me in February. I also can make calls with the 2 Sims that came with the router, when you call they don't answer, when you request a call back, they never call you, I finally got hold of them this morning but the agent greeted me and the call got cut and she never bothered to call me back despite logging in my cell number, I am starting to regret the choice of choosing rain again.