My my phone s21 can only be used in globe sim

You probably have a pre-paid handset/cellphone: pre-paid phones are partly funded by the service provider which in turn, as standard practice, 'Network Lock' the handset.

To use other SIM from different service provider, you can try to request the Network Unlock code from the original network provider: it will be free if you meet certain conditions (such as a minimum total recharge amount) or for a Fee otherwise (this is for them to recoup some of the 'real' handset cost).

Depending on your handset model, at your own greater risk, you can also use a reputable third party Cell Phone Unlocker: always ask the unlocking costs and refund policy.

Hope it helps!