I am a T-S ground seniority driver. This past Monday apparently a large amount of M-friend drivers had called in. With none left our supervisors started calling T-S drivers in. Me enjoying the sunday night having a drink was NOT expecting a call on Monday. That being said I was not around my phone when they called to have me work. My supervisor then counted it as a call in. Not entirely sure on the rules as far as forcing in. Talking to my supervisor they and union steward they put the call in on "hold"(not entirely sure on the meaning of that). I don't call in, so I don't care about the call in, but I foresee this being an ongoing issue where I am forced to keep my phone on and not have a drink/ be prepared to work every Monday. Any additional info would be much appreciated!