600 off when adding a new line

When adding a new line and buying a phone for it, tmobile offers $600.99 off the phone total cost. It is sometimes lower for certain phones but there is generally a discount when adding a new line. Is this offer limited to one line only or can it apply multiple times?

I´m trying to add two lines to my plan for a total of 3 and I´m getting a new phone for both of those lines. Is the deal limited to the first line I add or can I use it twice? 

Thanks!