billing issue

i went to a cellc store in clear water in december 1st week it was the 2nd December 2020 To seek a data sim because my rain network was not good enought anymore. walking into the store i saw a data sim plan for R299 and i decided to rather take up the one for R399 per month. i was advised i could cancell anytime. i forwarded docs and it was approved. I was called to go sign the agreement and i was still on duty but i took tome off to rush there as it is just 5km away from my house. I then recieved a statement that showed data amount that had R900 And something and R800 that i do not understand i called the customer care they said that is the simcard data plan i took up. mind you i have a device plan ending in march with cellc that i have been paying without issue and due for upgrade and i pay R538, Why would i take a sim card contact for R900.00 when i paid R250 monthly with rain and to take a 5G with rain would only cost me R700 unlimited? i took up the R399 50gig day because i thought i would last which i cancelled even because it only lasted 2 weeks and went back to rain to obtain a 5G unlimited which is working fine. i am in dispute of the statement and i am not going to pay that R900 and R800 on the statement which i do not know what it is for and request that cell c rectifies the statement so that i pay what is due because i hate unpaid debit orders in my account. i will not have such funds ever to pay cell c and now my cellphone is affected and not paid because it is one statement. i initially was in arrears for december due to overspending in december and i already left funds for that to debit twice and then the data sim but the debit order failed again due to an amount that i did not leave funds for as i did not anticipate that kind of a debit order to go off my account.