card to 64k sim card

Gadgets and Devices Mobile Phones & Tablets
1

Hi all,
Does anybody of legally getting one’s sim card upgraded to 64k sim card ?

2

whats the diffrence b/w the two?

3

You can ask for a replacement right? I got my Airtel SIM that way

4

Checksum, details please.

5

The BSNL 3G sim is a 256k sim card.