Netflix plans

I was paying for Netflix standard with ads and at one point xfinity gave me an upgrade to standard, no ads at the same cost as standard. About 2 months ago, I received a notice on my TV that i could get premium for an additional $7. However, when the bill came I was actually being charged an additional $18. I want to go back to what I previously had. I spoke w someone today and they said they could do that. They didn’t and now I  have ads. I shouldn’t have to go back to having ads when I didn’t have them two months ago and was deceived by the prompt on my tv that it would only be $7 more for premium. Who can correct this?