Query data cost when my line has been cut

Have overdue account with cell c ive contacted them more then once to query some of the bill also to make arrangement no one gets back to me. The first month i skipped them my data usage has been cut but im being charge for every month or months after i can not use the data also i lost that sim but i have another contract with them and i do call them from there thay have all my details and never mention this over due account like i said i want to make paying arrangement but they say ill get a call i just never do.