Beginning Wednesday, February 13th T-Mobile will offer a promotional family plan add-a-line option with $0 Value and $5 Classic add-a-line offers. This add-a-line promotion represents a $5 savings each month until January 2nd of next year.

Existing customers can take advantage of this opportunity by switching to the Classic or Value family promo rate plan, which does come with a contract extension however. The $5/$0 add-a-line offer is available on shared limited bucket family plans and the 500 minute add-a-line option for unlimited family plans. Unfortunately, according to the above image, unlimited add-a-lines are not eligible for a discount. In other words, the primary line can have unlimited minutes, but the second-fifth lines are not eligible for a discount if they choose unlimited minutes. The good news is that they will qualify if they opt for the 500 minute add-a-line option. Get it, got it, good?

This offer will run through March 23rd, which is timed nicely with the rumored launch of the iPhone and Value Plan only atmosphere on T-Mobile. Coincidence? Maybe.