I wanted to change my network operator. In the shop they told me they'd send me a new SIM card and until that wasn't activated I couldn't use my phone. So, I am wondering, why is that? I can still keep my number. Isn't that enough information for the provider? I thought my bills were assigned to my number… Why do I have to use a new SIM card? Now, I have to wait a few days until I can use my phone again… :(
Thnx for your help
asked 26 Oct '12, 10:11
SIM cards store information that is specific to a network that is used for the identification and authentication of subscribers on a network, which include the International Mobile Subscriber Identity (IMSI), the Integrated Circuit Card Identifier (ICC-ID), the Authentication Key and the Local Area Identity. So, obviously without a SIM card you couldn't use the network. SIM cards also store other types of information specific to a carrier, namely the Short Message Service Center (SMSC) number, the Service Provider Name (SON), the Service Dialing Numbers (SDN), value added service applications and other parameters. SIM cards come in at least a 32 KB capacity type and a 64 KB capacity type. Both allow the user to store up to 250 contacts on the SIM, however, the 64 KB card supports 80 Mobile Network Codes (MNCs) where as the 32 KB card supports only 33 MNCs.
Network operators use it to store information on selected networks, generally used when the SIM card is in a roaming area—away from the home market. The network operator issuing the SIM card connects the SIM to a preferred network to take advantage of lower prices and/or a better quality in the network, rather than paying the network operator that the SIM card recognized first. This does not mean that a SIM only connects to 33 or 80 networks. This means that the issuer of the SIM card specifies that the SIM will connect up to that number of preferred networks, and if a SIM is outside of the these specifies networks it will connect to the first or the best available network. With the introduction of the SIM card, Mobile Virtual Network Operators (MVNOs) were able to take advantage of a new and significant business opportunity by leasing the capacity from one or the network operators and providing a SIM card to their customers instead of owning or operating a network of mobile cellular telecommunications. MVNOs, like SIM only, operate in over fifty countries and account for roughly ten percent of all mobile subscribers in the world.
Some mobile phones are locked to their carrier SIM card, which means that they can only work with SIM cards from these carriers. This practice is more spread out in markets where mobile phones are heavily subsidized by the carriers, and the business model relies on a contract binding customers to stay with the service provider for a minimum period of one to two years. This gave birth to a new kind of businesses that offer to remove the SIM lock from a mobile phone, making it possible to insert a different SIM card and use the mobile phone on any given network. I hope I could explain to you why it is absolutely necessary to had a SIM card, at least for now. I'm pretty sure before long the market will offer another even better solution that will make us all buy new phones again ;) Take care
By accident I found this page and the answer above seems a bit long winded. My short answer would be:
Your SIM card is used to identify you on the mobile network. Providers have their own IDs which they put on their SIM cards. I think that technically it would be possible to link the SIM card of your old provider to your new account with the new provider, but this is too much (bureaucratic?) hassle. Your mobile phone number is only assigned to you once you are connected to the provider's network, for which you need a SIM card.
Anyway, hope this helps someone!
Source: work for eensim