MTN just doesn't do anything to reduce signal outages

We are a mine halfway between Delmas and Bronkhorstspruit. The only reception we have on the mine is MTN and they have a tower on our premises. We rely on this for all our communication, voice calls as well as data. Over the last year or so, we have constant signal loss to the extent that we are finding it impossible to run the business because we are not able to communicate effectively. This is also causing an extreme risk to the safety of our employees, since alot of the employees are doing high risk work and would not be able to call for help because of the poor signal. We had an armed ******* on the mine a couple of months ago and the security battled for over 2 hours to get hold of us to inform us of the incident. One security guard was stabbed and they could not even call the ambulance. I have complained to MTN numerous times already, to no avail.. They just call after a couple of weeks to find out if the problem is still occurring and when I tell them that it is still an issue, they promise to resolve it and call me back, which they never do... I can not believe the "don't care" attitude of MTN towards their business clients, especially since it has such a big impact on our business and safety of our employees.