Described are call handling methods performed by a carrier network or client stations. A method performed by a carrier network includes designating rules for call handling for an account, receiving first and second voice calls for the account, wherein the voice calls may be either an incoming calls or originated calls and handling the first and second voice calls for the account based on the rules. A method performed by a client station includes receiving a first invitation to a first call, responding to the first invitation causing the first call to be active, receiving a second invitation to a second call while the first call remains active and responding to the second invitation causing the second call to be active and the first call to be on hold, the client station is prevented from originating a call when one call is active and one call is on hold.