Mtn
Poor Cellphone coverage and dropping of calls

We have 16 cellphone contracts with MTN (Nashua Mobile)
It is a voice Call problem. Calls are being dropped, numbers are unavailable even if you make calls between 2 people standing next to each other.
The problem is experienced at all times.
The problem is experience every where. Atteridgeville in Pta West, Krugersdorp, N4 towards Witbank, Midrand, Olievenhoutbosch, Ellisras, Trichardt Mpumalanga and Bronkhorstspruit, Boksburg South & Jhb South.
The problem is experienced using a Bluetooth car kit or handset, indoors or outdoors.
Make and model of handset / device we mostly use are IPhone 4 or 5
The problem has arises over the last 4 months. We are a company with 16 MTN Cellphone contracts. This problem is hindering our day to day progress which is also affecting our long term bussiness with our clients.

We have written Nashua Mobile a complaint letter on 11 July 2013 but have not received any feedback.