Authentication Problem with WPS Disabled?

[adkaush]

I have been told by my ISP that someone is hacking my wireless connection and using the internet. They established that by making my plug the internet wire directly to my computer. When the wire is directly plugged into my computer (bypassing the TPLink router), the internet works absolutely fine. But when the wire is plugged into TPLink router, the internet goes pretty slow.

So, they advised me to disable the WPS which is known to be hacked easily. But when I disabled WPS, I can't connect my Redmi Note 2 and other cell phones to the wireless network. I keep getting Authentication Problem and also, my phone keeps asking for the WPA2 PSK security key over and again. The phone will just not connect to my TP Link router wireless at all.

I have also tried to disable the MAC filtering in my TP Link admin .. also tried to Allow MAC Filtering and hard coding the phone's MAC address .. but none work.

Am I doing something wrong here? Am I not supposed to disable WPS? I really wish to get rid of this hacker that keeps hacking in my wireless network and keeps steeling bandwidth.

Please advise what should I do. Appreciate your help a lot!

Also, I'm new to this forum. If I posted this question in the wrong forum, I request the admins to move it to the correct forum. Sorry about the botheration.

Thanks.