Paying for all extras that was not included, without knowing it!

I have just finished a 2year contract with Cell C.My phone an XR i-phone is still perfect. I just needed to have a contract for phoning and for data. I purchased data and minutes just to discover that the 945min where 900min only for cell C phone calls the other 45min to other networks. I further on I purchased Data for WhatsApp phone calls which I learned I was billed for overseas calls while using Data when I did not have wifi, so I am paying for data and overseas calls.I can only use WhatsApp to phone my children overseas. I then signed a Black |Friday special.Again the minutes that I thought was talk time only go for certain calls. You have to buy airtime for certain numbers, aswell as minutes, as minutes takes you further and you can phone other networks. When Adt phoned me for the alarm I could not return their call, I was cut off, as I did not purchase airtime. At present it seems with all the ad-on's I am paying more or less what I paid before when I was still paying for my phone. At this stage you never know if you have calling time or not! This is unacceptable!! I am totally frustrated and disappointed in Cell C as by the looks of it they are not honest in their dealings with their clients.