Upgrade SERO to Everything Family?

[gbm85]

I currently have three SERO lines totalling $90/mo.

I found out my company gets a 25% discount so I can upgrade to Everything Data Family on all three lines for only $112/mo. Figuring in everything that's included especially Sprint Premier, it would actually be a better deal.

So can I upgrade my account from SERO to Everything Family without extending any contracts? My contract is up in 3 months, my wife's in 17 months, and her sister's line still has almost the whole 2 years left.

My account is on Ensemble if that makes a difference.

EDIT: Oh yeah, I'd like to keep our current phone numbers too