Missing payment

I've been having a problem with cell c for the pass month now.Cell c has informed me that i had not made a payment for one month.I've then explained to Cell c that, i have made a double payment towards the end of september of the amount of R700.00 to cover september and October.24hrs later my services has not been reconnected.i called Cell c up and they informed me that i still owe a R98.00, in the begin of October i go and make a R98.00 payment at Nedbank as my DD had to stop which initial i had setup with them when i took out the contract with them.My services goes back on again,At the end of November i make another payment at Nedbank.my services continues,I then get a sms from Cell c that my services will stop due to none payment..i call them up and explained again i have made payment in December of R400.00 services goes back up again,few days later i get a sms again informing me that account has not been paid,services will be stop, i call up again and they tell me that i've not made payment and need to send them prove that i made full payments on my account..Now i dont have any slips to prove as i through it away.Nedbank cant help me getting the slips.Wot do i do help please