Wi-if drops whenever we answer a phone call

[Annav99]

We noticed our WiFi dropping a lot more recently, thought that due to harsh weather it was normal, or if a wire had been accidentally knocked. Today however we noticed that when we answer phone calls the internet drops completely, then after the call has been hung up it eventually comes back. Has anyone had this before and how did sky fix it please? My mother in law answers an awful amount of phone calls a day 

[Highlinder]

@Annav99  Does the phone socket have a filter in it or fitted to it as a filtered faceplate that the broadband router is plugged into?