Frequent Disconnections and wild fluctuations in SNR and data rate value

My PTCL DSL phone line is directly connected from DP to my modem/router and every now and then my internet gets slower and i get frequent disconnections because my SNR Margin and other values drop. To get the values back to normal, i connect the phone cable to my landline and then call myself from my cell phone. I then reconnect the cable to my modem and restart it. This get the values back to normal and my internet connection stays stable for a few hours before i have to repeat the same action. My dsl stats when normal are:

Downstream Upstream
SNR Margin : 26.1 9.4 db
Line Attenuation: 25.9 16.4 db
Data Rate: 9216 1090 kbps
Max Rate: 21088 1109 kbps
CRC: 0 0

These values drop significantly after sometime like my SNR Margin gets as low as 7 or 6 and data rate drops to 2000 downstream etc.

I have checked my phone/dsl cable and it doesn't have any joints and i don't use my landline phone so i connected the cable directly to my modem. I tried using splitter but that didn't fix this issue. I am guessing this might be static or some kind of interference around my cable that develops overtime and calling my landline fixes it. I will appreciate any help you can offer.

Check the joints or cable switches from splitter aas well.

Else Lineman can resolve the issue in few minutes. Either Cable from pole or cabinet needed to be reinserted into slot or there is malfunction in cable joints

There are no joints in the cable and i don't use any splitter. the cable is running directly from the DP to my router/modem. I had a lineman check the entire length of the cable and he found no issues.