Look at your current usage and double it at least, triple is even better because coming half way through the month and running out of bandwidth is probable the worst thing you can do for your website, your users will probable desert you, if they see it isn’t online for a day or two.
I can draw your attention to
hostwinds.com ssd litespeed web hosting solutions.
You will find out the availability of their systems administrators and send them a support ticket and see how fast they respond.