ATT Phone as Modem - Speed?

My contract with T-mobile expired today.

I need a phone that I can use as modem to get on internet on my laptop.

Currently, I only pay $5.99/mo for the T-mobile data plan but speeds are too slow..I know sprint, Verizon, ATT have good speeds.

So, question is:

Which network provider has the fastest internet speeds ?

I'm basically choosing between sprint, verizon and ATT ...just want to know which one you all recommend out of the 3