A naif's question on SIM cards

oldwiring

ATM I am using a Nokia 2720 with ASDA Mobile, PAYG but am thinking of upgrading to a smartphone.

Are cards compatible between makes of phone, types of phone; between ordinary and smart?

How transfer personal data e.g phone book across?

Skint_Catt

Sim's are transferable (except to the iPhone), but sometimes phones are not! Phone's can be locked to a network, so you either need to ensure the new smartphone is from ASDA mobile or 'unlocked'.
A 'smartphone' will need a data allowance on the tariff too if you want to use the internet browser/download apps - something you may be able to add to your PAYG tariff if you don't already have it (I'm not aware of the functions of the Nokia 2720) - you need to talk to ASDA Mobile to see if this can be done.
With your phone book - this all depends on each phone. Your instruction manual should be able to tell you how to ensure your contacts are saved to your sim rather than on your phone memory. If they are on the sim, then they will appear in any phone you use.
Hope this helps?
C xx

clemmatis

Sim cards vary in size/type, it's best to get the right kind (size) rather than try to adapt them yourself (IMO)

http://support.vodafone.com.au/articles/FAQ/What-different-types-of-SIMs-are-available