Here is my situation.  I have three smart phones and 1 voice flip phone. Two years ago I got the phones cheap.  Now 2 year contract is up.  I am going to switch to their plan where I pick shared data, then add the phones.  Will save a bunch of money as lonng as I get my data usage down.  I will not be getting new phones, just use what I have except my son bought a new Google Nexus phone that he is using.  From what I see now it is best to save your money and buy a phone when you want to get one ( or need one) and avoid the monthly payments for phone.

From what you wrote I may have to question the plan but I do not see how you will save money when getting a phone and sign up for service.  To me it looks like now you can do both for two years or just the pay for service as a monthly cost.