Useless home router.

I went to Telkom Jabulani mall needing a home router/Wi-Fi rather for work purpose. I asked the consultant to thoroughly explain to me as I am not fami**** with network for work purposes. I also told them I use many app and I will need connectivity with high/fast speed. The consultant then said the one with the best speed was a 10mbps. I took it cause I mean like I said I know nothing with networks so I trusted the consultant only to find when I get home and start working the network is slow and some applications are not working. The reason I am sure that the issue is with Telkom it is because when I switch to different network provider everything works perfectly fine but when I connect to the Telkom router everything is slow and some apps are not working. I was specific to the consultant that I need this for work purpose it was not for fun or entertainment. I only have 4devices connected to this router but the way it's so slow you would swear the whole city is connected to it. I don't want this router anymore, I cannot be paying every month for 24months for something that is so useless, the price of this router is too high for the speed it has. It's either I get a proper router or we cancel this. Should I not get any assistance I will be taking this to the ombuds because consultants are there for a reason, they need to assist customers and explain thoroughly.