MTN Branch and Call Centre cannot explain their products

I'd like to complain about MTN people don't know their products and waste people's time. I signed a promotional contract on 30-Sep-2017 (20GB+20GB+extra 10GB for 3 months ********** The next day when I go and fetch the sim and device, I checked the data balance and it only gives 9GB and 4.33GB night time. I asked Moe the consultant about this and he say this is due to prorata cos billing is on 13th. However, when I calculate the prorata, the calculation is not like what is advertised of (20GB + 20GB, not even with the additional 10GB). I asked for an explanation and no one from the cresta branch or call centre can explain to me the prorata calculation and the prorate charges. I eventually didn't take the sim with device and ask the manager,Victor, to find out what is going on and then contact me, so I can understand what I am buying and pay for it. This weekend, I spend about 2.5 hours in the MTN shop for nothing, really disappointing! MTN should not sell products that cannot be explained to customer in detail. I am so glad that I checked out the balance, otherwise I will be another victim of mis-selling! I hope I will get a response from Cresta branch. This is really not a good way of doing business when people are selling products which they cannot explain.

My contact detail is ********** 367 and I hope someone from MTN can assist me on this.