ou do not need a phone to get the internet - cable. Wifi, mobile do not use the phone line. But ADSL stands for Asymmetrical Digital Subscriber Line, and Subscriber Line is old fashioned speak for a telephone line. Digital is obvious and Asymmetrical means that the download speed is different to the upload speed. In residential connections you get a download speed many times the upload speed.
The commercial version is SDSL, with the first S meaning symmetrical – download and upload speeds the same.
You do not need to have a phone connected, but in any socket with equipment connected you need a micro filter. The service supplier will probably give you two of these.