Plusnet cannot help !!

[#1]

My internet has been dropping for two days and today the phone was crackling. I got through to plusnet today and they could see that there was a problem occurring  Then they said that they could not help me as they would be unable to run tests as I have no mobile phone ?  They said that my call would be cut off from my landline and they would not be able to call me as I have not got a mobile phone.  I have never heard anything like it.  My problem is still there.  I have had this many times over the years and usually engineers come and find nothing, It always comes back on its own and is fine for a while and then starts dropping again.  ALL the indoor tests have been done (master socket, filter connections etc.)  What am I supposed to do now ?.

[#2]

UPDATE.  My internet is still on and off and only reaching  .49mps.  I did not want the engineer in my home as I am elderly and am ''isolating'' at the moment.

I know that there is no fault in my home or on my property as I have had this recurring problem for years now.  It has always gone back to 'normal' after a couple of days and no engineer has ever found a fault within my property.  What am I meant to do now ?  I have a new router coming and doubt that will make any difference.  Openreach state that there are no outdoor problems and everything is good indoors.  This is getting silly now.