World Voice Link...won't answer phone!

I too bought the free 30 day trial offer and was told they woulld send voucher for pager and about the 1 time $29.95 charge.
I was told I could cancel before the 30 days and would have no additonal charges. The only way to cancel is to call the 800 number and no one answers. I have tried for over a week to cancel by calling # and no one will pick up. I am stuck. I am attempting at this point to get the phone company to not charge any additonal monthly. However, until I can do that, they will keep charging my phone bill, actually my son's phone bil

Is there anyway to stop these people?...and get money back? SLB *I will also try to send a registered letter, however by this time, the 30 days is up and there is no date on their letter. Also I am feeling it is probably a phony address.