I wouldn't deal with anyone over the phone like this. She can almost certainly get a better deal than she has at the moment with BT but she should use a price comparison site to get the best deal, then she should check on customer feedback
Haven't heard about the name of the company either but most probably a new company in the market offering services via phone. Still if it were me, I'd still go with BT since it is trusted already. Just be aware of agents calling you as there are a lot of scams these days.
http://uk.reuters.com/sectors/telecom http://www.comverse.com/about_comverse_vas