Being bil**** for something i dont use

I had 2 mtn sim contract one was lost last year but contract was not ended i called to close sim than since last year i was paying i though after my contract ended they will stop billing me for TT lost sim but till now they still billing me my complain mtn can see that the sim was last used last year why they didn't stop billing me for that sim when contact ends n let me continue with other one i feel treated bad I'm their client they must check which one is in use currently not just bill for business purpose since June till now still billing me for something I reported why can't they review that's bad. I forfeit everything every month on lost sim they we're sopposed to stop billing me immediately when contract end cos its not in used no sim swap was done just saw my statement yesterday.