Bad service

I took a device in 2019 which was a Samsung Acore which cost R105 every month and was debited till the last day of the contract to my suprise I see a credit rating that I owe them R18000 when ask was it is for am told for I device I took and I didn't advise them that I want end contract I don't understand how when they stipulated it is 24 months please that amount from my credit report I don't owe guys nothing it's 2023 only now you guys see that I owe you cellc is really a **** cause not only me but my 2 friends I referred to you are also going through the samething