According to multiple posts on Reddit, T-Mobile is bringing back its free line promo. T-Mobile free line promo is backAccording to user reports on Reddit, T-Mobile has sent emails and text messages to customers informing them that they are eligible for the free line promo. If there is, then you might be able to get an extra line for free. For starters, if you accept this free line, you may never qualify for a free phone, upgrade, or any other promo in the future. However, if you’re merely using this as an extra line for business purposes, we suppose it’s not a bad deal.