New Tire Noise - Prius Persona (2013)

My Prius came with Bridgestone Turanza EL400-02's (P215 45R17) which lasted 70K miles, I replaced them at Mavis the other day (big mistake, another story for another time) with Continental TrueContact EcoPlus tires which has much better ratings all around according to Tirerack.. The problem is I get this humming noise that sounds almost like engine noise between 55MPH - 65MPH... I did not have that noise before.

I went back to the shop and they told me the wheels were balanced incorrectly, they re-balanced them but I still have the same problem. They told me the rims were bent, but said that wouldn't create the noise I hear.. Plus I didn't have that noise previously... Today they told me there's nothing else they can do and told me to deal with Continental.

I'm so annoyed.. $716 for these tires... Anyone have any suggestions?
I already spoke to Conti who referred me back to the shop. I'm going to go to a different Mavis since the manager of the current one lied to me and then to Continental... (luckily I have this recorded on my phone..)

-Keith