UNHAPPY WITH UPGRADE PHONE - HAUWEI P10+

Good morning, I would like to query the following. I received my upgrade phone, a Hauwei P10+ during August 2017, since receiving it, it has been freezing and had overall slow performance, I am very unhappy with this phone and I do not want the same phone back again once MTN has fixed/replaced the phone. Please could you inform me, as a contract customer of MTN, that I am able to ask for another phone? Thank you.