In a previous post I've put down my thoughts and practical experiences with roaming through Europe and staying connected to the Internet with prepaid GSM/UMTS SIM cards. While it works quite well there is the disadvantage that a different SIM card is required in each country. So I was asked how people can reach me when I change my SIM card every couple of days!? There are several strategies:
1) I have a SIM card dedicated to voice calls. My friends only know this number and the SIM card is in a seperate phone.
2) If I only want to carry one phone I activate call forwarding unconditional on that SIM card to the SIM card I am currently using for Internet access in a country. There is one problem with this approach: Some prepaid SIMs by default forward calls to the voicemail and this call forwarding can not be deactivated. So I always pay for an incoming call no matter whether I pick up or not. So I ususally prefer to carry two phones.
3) I have an ISDN fixed line at home. While I travel I forward calls to the SIM card I use. There is a web interface available so I can change the call forwarding from abroad when necessary
4) Skype is also an option, though I haven't tried this yet: Get a Skype in number and then forward the calls to a mobile phone number when you are not online.
It's a pity one has to go through all of this just because pricing models of operators prevent people from using a single SIM card for all purposes. But who knows, one day...