There are also two types of dual SIM phones: regular dual SIM and active (or dual standby) dual SIM. In active (or dual standby) dual SIM phone both SIM cards are always active, and can receive calls. In regular dual SIM phone only one SIM card can be active at the same time.
worked like a charm. first you have a contact list on each sim card, and one in the phone, so you can store more numbers than you can remember names! when making a phonecall you just selected with which sim you wanted to dial out. and you could set different ring tones for each sim card, so you know in advance if it's bad news or not
oh, and at 5 o'clock, you just deactivate the work-sim!