Once you've entered in the details of your SIM and gone through the activation steps, in most cases you'll be able to start using your amaysim service right away.
Number transfer timeframes
If you're transferring an existing mobile number from another provider, your SIM will become active once the transfer process is complete. Most transfers will become active within a few hours, however the process can take up to 3 working days depending on which provider you’re switching from.
During the transfer you can continue to use your current provider's SIM. Once it stops working, that'll mean your amaysim SIM is in the process of being activated.