Dear, “Dear, Pan” (thank you Shukrullah :). I think, it is incoming call to your roaming subscriber having Call Forwarding SS (CFU or CF unReachable) in active state (You may check this in HLR). When HPLMN GMSC receives Forwarded-To-Number from HLR it creates CF record for Forwarding Subscriber and the rest part of call is considered as outgowing from the Forwarding Subscriber (your Roaming Subscriber). And he is in charge of this part (He pays the bill).