Not provided with full information to make decisions

I upgraded my contract with MTN on the 15 June 2017 and took Hauwei P9 lite since it's a dual phone and I needed that. To my surprise, after I've signed and my sim was put on the phone, I wanted to put my other sim and I was told that with MTN you can only use one SIM. I feel that I was deprived the right to make informed decision by Huawei and MTN because I was not told before hand. I googled the description and features of this phone before going to the shop and I wanted this one specifically for dual SIM but now I'm not enjoying the benefits of having this phone. I contacted Huawei and I was told that, yes, with MTN and Vodacom it only uses 1 SIM yet they did not mention that when you check the description and functions of the phone. Can I please be assisted on this matter. I have a phone that I'm not enjoying having it.