Getting only 5% of the advertised speed

I signed up for 900 mb plan but through speed testing on Comcast speed test and speedtest.net, I'm only getting 50 to 60 mb on download. That's less than 10% of advertised speed! I'm using TP Deco AX3600 with Arris S33 modem. I tested both on my phone and laptop, but getting similar speedtest results.

Please help!