MFA Springfield defective Smart TV

Purchased a Telefunken smart TV from mfa springfield branch. The network keeps disconnecting. You can not even play a song or watch a movie without the network dipping. I've contacted my fibre service provider several times. They have sent guys out to check the lines but it's fine. I even changed my service provider and still it disconnects.

I'm so disappointed. Why do they sell appliances that are defective.

What do I do as this TV is only 5 months old?