Poor service from MTN

We recently moved and the cell phone reception is poor, only allowing us to SMS but not receive or make calls. We contacted MTN on 23 February to ask if MTN would be able to improve the signal as we have signal some 100 metres away from our house. We were advised that we would be contacted in 12 days. Nearly two months later we have heard nothing despite ringing nearly every week to see if anyone is going to make contact. Each time we are told our query is being escalated. All we are asking for is someone to contact us/visit us to advise if the signal can be improved. If not then we will try and make an alternative solution. We run a business and do not have a land line, thus the cell phone is our only means of communication. We are desperate to resolve the situation, with our without MTN, but we just need to know if there is anything they can do from their side before we pursue an alternative. To go two months without any contact from MTN shows a complete lack of service and support for us their customers. We have been with MTN for 15 years, but will be reconsidering our service provider once our contracts are up for renewal.