Question about my free lines

I'm on T1, I have the 2 free lines from magenta Friday and the one free line in March plus 2 more lines that I pay for (5 lines total) I was wondering if adding a 6th line would result in me losing my free lines due to being moved to a different tier plan. I don't exactly know how t mo divides them up but isn't going from 5 to 6 a different "plan" ? (I'm adding the extra line to take advantage of the BOGO for the s8)
Edit: typo