Netgear N300 WIFI Cable modem Router dropped the internet speed from 25MBPS to 7-8 MBPS

Speed dropped from 25MBPS to 7-8 MBPS which is getting difficult to stream one device. When reached out to Netgear technical support, they started with informing about extended warranty to support even before understanding the problem. Asking to pay $ 89.00 for troubleshooting. Please find the steps taken by myself to trouble shoot:

1. Connected directly using cable, downloading speed was 28.38, when tried with WIFI, it reduced to 4.39 - 7.82 mbps. This explains modem is functioning fine.

2. Connected neighbors router N600 to modem, downloading speed increased to 25.72 mbps. This explains problem is with the internal router.

3. I have not moved the router / made any changes, suddenly there is a drop in the speed which is unexpected. When asked for help, they start with payment of 89.99 for technical support.

4. I have gone thru every option under 

http://kb.netgear.com/app/answers/detail/a_id/1114 and 

http://kb.netgear.com/app/answers/detail/a_id/1110

which did not resolve.

5. Under NetGear Genie, i have changed the channel from AUTO to 1 / 6 / 11 and tried all the setting changes, still did not work.

6. Finally i decided to do Factory reset which ideally gets back to first day, still the speed is same.

I still have the hardware warranty but unable to use even when i have tried all the possible scenario's. I get new Router for $ 75.00 from Netgear which will work as i have tried my neighbors.

Please help me in resolving this problem as technical support needs to be provided for product which was working fine and suddenly stopped working due to some update / hardware issues.

Thanks

Prateek