Mondo + MTN do not help customers

I agreed to a deal with Mondo and MTN for a contract laptop. The main reason to a take this deal was a promised R40 000 short courses study voucher. I asked during the call 'can i use this to study anywhere meaning any institution', they said yes. but till today it's rejected by many institutions The laptop arrived without the sound, i though maybe it's only the setting i will mange to correct it but i couldn't and i took it to MTN shop which they tried but they told me 'it's not settings but drive, as a result i should call the call Centre to pick it up and fix it. The call centre asked me to take it back to the shop and the shop will book it for fix or send it to them. It has been up and down on different MTN shops, emailing the call Centre but I am still with the laptop without the sound. Worse I have never missed the payment but no services.