T-Mobile promotion offers new and existing customers a free third line

T-Mobile's Deals page revealed today that the carrier is offering a free third line to new and existing customers. The promotion is cleverly titled 2019 Spring into Summer 3rd Line on Us and is available from T-Mobile's retail locations and website. Here's how it works. If you're a new subscriber, activate three new voice lines on T-Mobile ONE, and the third one will be free. Existing T-Mobile subscribers must have one postpaid T-Mobile ONE voice line active. If they are subscribed to a different T-Mobile plan, they must first switch to T-Mobile ONE. Then, two more voice lines must be activated with the third one free.

Once you've successfully qualified for the free line, you'll receive a text message confirmation. Within a couple of months, you'll start to see the bill credit for the free line appear on your monthly invoice. If the credit doesn't appear on your first statement, you will receive twice the credit on the second invoice.

There are some requirements. It goes without saying (although we will anyway) that you need to keep your accounts "in good standing" to keep receiving the monthly bill credits. If you cancel any line within one year from the time that you signed up for this promotion, the bill credit goes away. After one year, you must keep two paid T-Mobile ONE voice lines and the lines activated during the promotion in order to keep receiving the bill credits. There is a limit of one free voice line per account, and the bill credit covers a basic T-Mobile ONE plan. If the free third line is subscribed to T-Mobile ONE Plus, you have to pay the difference between the basic and "Plus" plan for that line every month.

Some T-Mobile plans are not eligible for this deal, such as 2 lines for $100 plans, T-Mobile ONE Unlimited 55+ plans, T-Mobile ONE 9+ lines, T-Mobile ONE Amplified, T-Mobile ONE Military plans, and T-Mobile Essentials.

The deal is available now, and while it is offered for a limited time, T-Mobile has yet to announce exactly when the promotion will end.