The $20 may be for month in advance billing. It should say that on your actual bill online. Check it and it should have a little info bubble next to it stating its a month in advance charge in addition to your prorated fee. I just converted my wife onto my share anything plan and they charged me her prorated fee plus $40 line access for one month in advance. Sounds more like you need to read your bill carefully and understand it fully, not that they are trying to pull a fast one on you.