Although I can't really contribute to a solution. I can confirm that Walmart does indeed sell Huawei phones for Koodo Prepaid services. Up until recently I worked at Walmart in the electronics department. The packaging for the phone is absolutely Koodo branded.
I would suggest following Jonathan's advice. If you have a friend who is also with Koodo try putting your SIM in their phone, as well as put your friends SIM in your phone. This will help determine if it is your phone or your SIM that is causing the data problems.