dial *100#, go to Collect Call sub-menu and then 'manage whitelist' sub-menu....and add the 7 digit number you want to be allow to send you collect call...
now you will not be asked to press 1 to accept, 2 to reject etc...'you will just hear, wait while your call is being connected' till the initiator accepts the call...
adding number to whitelist or blacklist is free of charge....