ADSL : Only works when my phone is being used

Hello! I have a Serbian adsl internet from MTS. I've been getting problems with my modem/router. Every time someone from my family uses it, only then does the internet work/ it works for like 10 minutes after using the phone ( calling, recieving calls ). After not using the phone for like half an hour, my internet just doesn't work. Sometimes the " internet " light is on but the wifi/ internet just doesn't want to load any websites, and sometimes the internet light just goes away until someone uses the phone. I used a temporary " fix " by picking up the telephone and leaving it on the buttons so the telephone thinks its in a call. If anyone can help me, and if you need more details just ask!