What happens when you put one o2 sim then take it out then put another o2 sim?

When you insert one O2 SIM card into your device, it connects to the network associated with that SIM. If you take it out and replace it with another O2 SIM, the device will recognize the new SIM and establish a connection with the network linked to that second SIM. However, any data, settings, or services tied to the first SIM will not transfer to the second SIM; you'll need to set them up separately if applicable. Additionally, if the SIMs are on different plans or accounts, you may experience different features or balance status.