renewed my contract even though I cancelled it.

my name is Ryder Thabo Hlungwane , I went for an upgrade in the 2021 May for my cellphone upgrade and the deal I was incorrect then I return their phone and canceled my upgrade as well as but to my surprised they did not cancel my contract and it keeps on billing even now in 2023 May and my ITC credit rating is down because it shows I owe CellC for more than 12 month in arrears AND I've never used my cell contract number since MAY 2021 but they kept billing as it was not cancelled as per my request then, this was done at Cellc Southgate mall and it since closed down.