Plan Magenta

Hello Everyone.

I recently switched from the cheapest plan avaliable, the one that doesn't include taxes. (Forgot the name)

I switched from essentials plan to Magenta plan because with taxes the other plan came out to like $130.50 and the Magenta promo stated 4 lines for $140 it seemed like a no brainer, I made the switch only to find out threw customer service that THAT 140 Magenta plan is for NEW customers only.. so during my chat with Customer Sevice I asked "so essentially I have to cancle my service with tmobile..  and rejoin again so we can get the actual $140 plan? She stated well... I'm not telling you too..."

So my question is, if I go down to tmobile and follow threw with my plan of canceling Magenta plan (prior customer) 4 lines, walk out the door, turn around and resign up 4 lines of magenta with tmobile, is this possible? 

Will tmobile try to tell me some old school cable company crap about having to wait 30 days after service cancelation? 

If anyone has any information of past experience like this, it would greatly help my situation!

Thank you again for your time!