Cell?

I don't know if this means anything but here's an observation. Red has disguised phone number by labeling it "Nick's Pizza" when he calls Lizzie's cell phone for two seasons of the show. He has frequently used "throw away" cell phones while conducting business. He goes out of way to make sure his calls are not traced. Why or how does Tom have Red's cell phone number in the season 2 finale? Tom calls Red on his cell phone to offer his assistance to Liz. Tom no longer works for Red and even when he did, Tom talked to the Major...not Red. I'm quite certain Red doesn't want to hear from Tom. Why would Red let his cell phone number be known to a person he does not trust? I'm curious to know if there is another reason Tom had his number...such as "You're my dad?" May seem silly but give it some thought.