Good speed of the network but nobody is able to assist with intermittent service

I have taken a data contract with MTN in June last year. Whilst the speed is great, the network has not been stable and is intermittent. Sadly, trying to get MTN to address this issue has been nothing short of frustrating. The voice prompts firstly dont work and pressing zero to speak to someone gets a ïnvalid entry" response. After gettgin through to MTN which perhaps for 4 or 5 times now including accounts, retentions, networks and technical, staff simply provide an update on their system without getting back to you. Their response has been that my settings had to be manually configured (how do you this with a sim inserted into a modem), or there is no problem. I have been directed from one department to another with no person being able to give me clear response. To top it off - 40GB of data was depleted in a period of 10 days (and I am not certain how this happened) When trying to top up using the APP, only after payment goes through do I get a message that data will only be loaded on my account in 2 days. After more than 50min on the phone today, it was difficult to justify waiting any further to cancel this contract. The speed of MTNs network is great however the network is less reliable than you think and MTN's customer service needs to reevaluated.