Impossible to get customer service on the phone

I have been a Cell C customer for years and have a the pinnacle top up contract plan of R105.00 which for years was only limited to the R105.00. I have noticed that they deducted a R180.00 and when I try do phone the call center I can't get hold of anyone due to them requiring you to add a service pin which they don't send. I even downloaded the app but it was no help.