Hathway / Gujarat Telelink [GTPL] — technical issues every now and then:- no internet access, no response from isp, low speed (max 20mbps for my plan of 50 mbps)

I've purchased 1year unlimited @50mbps connection from gtpl, chandkheda.
From the beginning i've had this issue regarding it abruptly getting disconnected every now and then and the router has to be turned off anf switched on again otherwise internet won't work.
Other then that i face issues like no internet because of some issue with "hardware connection at wan port" i complained when it happened the first time and it took them more than 5 days to send a technician who checked the router and all the stuff at my end told that the issue is from their end, issue got resolved, and just a month and a half later same issues, i complained and it wasn't resolved for 7 days, right now as of this moment i'm facing no internet because of "no response from isp" and tried calling their toll free number but no answer, also till date there's the issue of low speed compared to my plan of 50 mbps, i get max 20-25 mbps that too rarely, and have to turn off and on the router 10-15 times a day every day as it disconnects on it's own.