Pimsleur Approach review: sending & billing you unsollicitated orders

They sent me a supposedly Free Trial, which I could have refused within 30 days. However their invoice date was 1 Feb 2011, whereas I received their parcel only on 4 March 2011.
I tried to phone them immediately after receiving the parcel, since they did not give any instructions as to how to return the parcel; but was put on hold all the time.
Finally got in touch with them on Monday 7 March, and received their "approval number" (in my case:R-[protected]).
I now have to send the parcel back with FedEx, but am not sure whether I have to pay for the return postage or not.
To me it appears that their sales policy borders on fraudulence, making it so difficult or impossible to return their unsollicited parcels.
[protected]@yahoo.com