Can you use any sim card for a Sidekick?

[ashbarnes]

I currently have just a normal flip phone from T-Mobile but was looking to buy a sidekick.
Can I use the same sim card?

If not, where can I get the right kind?

[geeth]

Hi yes you can sure use your old t-mobile sim in the same sidekick mobile only if it is unlocked one.Else if the phone is locked to some other network provider then until you unlock it you can't free use it with your old sim .You can easily unlock your phone using sites like TheUnlockSpot.com here they are rendering unlock code for all mobile models at reliable cost ....After unlocking your phone you can freely use it with any GSM sim...