You can forward to
username@sip.voipcheap.com either from a DID or SIP account that allows such forwarding (Eg. IPKall DID).
I have tested this and received the call on the Betamax Windows client.
However, I was not successful to get call forwarding from Voxalot to the Betamax client. The call goes to the Voicemail of the IPKall DID.
Possibly Betamax may not be allowing such call forwards.