No Dial Tone or able to receive incoming calls

[RichardMackman]

Since December 23rd around mid afternoon the  dial tone has gone from my phone,  anytime attempt to call  from my mobile it says    ' number  not in use '   However  if  I  plug  my phone  back into the router  it will  function as normal again for a minute  then the  dial tone will go again.  I have tried  2  different  land line handsets, and 3 different connect cables from phone to router.

I need this landline  to function as I  teach from home and my students cannot call me now.  

[Daniel0210]

@RichardMackman 

You will need to contact Sky to report the fault. Take a look at this link initially. If a faults found it may give you an option of reporting it. Sky will then notify Openreach. Their target  fix time is two working  days from being notified. 
https://www.sky.com/help/articles/fix-phone-problems-start