Beware Voipo's prorated charges and customer service

I had a 15 month contract with them. When the 15 months was up, I formally cancelled my account and sent back their phone adapter in the mail. Yet Voipo charged me (on my credit card, whose number they still have on file) a "prorated" rate of $23 for the few days beyond the termination of my account that I still had their adapter. Two points:

1. It's not possible to use a VOIP service - or any service for that matter that involves rented equipment - up until the day the service expires, and return their equipment back to the service provider that very day. There has to be some grace period wherein you're allowed to return equipment without incurring a charge.

2. How is $23 a "prorated" charge? First of all, they got their equipment back within 2 weeks of the expiration of my service (I know because I was notified by the postal service). But even if they were charging "prorated" rates by the month, and not parts of a month, they don't even have a residential phone plan that costs $23/month. What kind of made-up amount is that?

And what's even worse is that, now that I'm no longer their customer, they're completely ignoring my email inquiries as to the fairness of this charge. There's nothing that's more of a turn-off than bad customer service and being ignored.

All I have to say is that they're sneaky, very sneaky. Bottomline, you can't trust them...