Calls and Data Problems

I have been a costumer with MTN for some time now and am on the edge of moving to another service provider. I pay around R1200.oo pm for my contract. Often when people try to get hold of me they say it goes straight to voicemail ( when my phone is on and signal is full ) The last couple days I have had to fill up my data and each time I purchase 1gig data , within 5min the data is finished. The data runs out without me even using my phone. Each time costing me R160.00 rand !!! I have done this many times with the same issue. I have also made sure that all my background apps are turned off and only use wi-fi to update. I have even tried to buythe daily bundle rate with unlimited data. Most of the time this does not load or gives bad results. For the price you pay and product your receive from MTN . I would say it is not worth it at all !!