Welcome to the forum.
Clicking on the filament type will allow you to change the type. You will need to change it to PLA and reslice the model.
If the filament you want isn’t listed, you might not have it checked in the list. Click on the Gear logo to the right just above the filament.
The important thing to remember is that what you have listed in Bambu studio for filament doesn’t have to match exactly what you have loaded in your AMS. Think of the filament in Bambu Studio as a “Library” of the filament you have available. Slice the model with the filament you want and then when you transfer the model to the printer you can match the filament to have you have loaded in the AMS.