Colloquial term for the mobile-phone service provider metroPCS. The "POS" stands for "piece of shit", because of the notoriously poor service and support provided.
My cell phone company is metroPOS. So my calls are always getting dropped, I can't even use my phone outside a certain limited area, and I can't usually get connected to anyone at the so-called customer service line. If I have a real problem I have to go into the office in person. But it's relatively cheap, I don't have to sign any contract, and I get unlimited calling within the contiguous 48 states. Too bad my sister lives in Honolulu, so I have to text her and have her call me back when I want to talk to her.