Why do sims cards stop working after 6 month?

[johnjoehannsg]

If it is more than a year you will not be able to use it again.
The networks think that you are not using the number and will put the number back into storage
Then then re-use the number.
I know this information as I used to work in that industry
Give the network a call and explain to them that you need the number reactivated. They may do so depending on how persuasive you can be and providing they have not already re-used the number

what about sending new credit to it remotely? would that work via the internet or another number

[longtipp]

If you do not topup for 6 months your sim deactivates, after 6 months you need to top up again even if you have unused credit, this will reactivate unused credit. If your card remains deactivated for 6 months I think they turn it off and recycle the number. If the sim is deactivated after 6 months, I think it still recieves calls but you cant make them. This is my understanding of vodafone, other networks may vary.