Why does my internet go off when my home phone rings?

We have the same problem and phoned BT today,they sent us to BT India and they said it's the phone so tomorrow it's back to BT landline people..It hasn't always happened,it's in recent months. We don't have filters just wireless broadband with the 2 phones recommended by BT to go with our set up so until we speak to them tomorrow,i can enlighten you no further............