Dish Network — Billing mistake

I have been a Dish customer for about 2.5 yrs.and have sent a check in the mail every month to pay my bill. My service started about $59 a mo. and went up steadily to about $139. I called and had them shut off some channels to bring it back down to $106. In January I got a bill for $126 for 2 months and a $10 late charge. I knew I had sent them a check every month, so I called for an explanation. I was put on hold several times and was transferred several times, after an hour or so I was told that somebody had paid my October 2021 bill by mistake, they discovered it and now I owed them for it. I have proof that i wrote and sent a check for that month, they tried to blame the postal service, my bank, and me for their stupid mistake.This is their mistake NOT MINE.