Can the iPhone 12 Pro Max use the two sim cards from different carriers each?

Hey there, Martirene.

Short answer is "Yes". But it must be a physical sim card in the phone, or e-sim that your carries supports. You can't not have 2 physical sim in your phone, unless your iPhone was purchased from China mainland, Hong Kong and Macao.

^https://support.apple.com/en-us/HT209086

For the US, you can have 2 sim on your phone, which is one physical sim and e-sim from your carries.

Please refer to this site: https://support.apple.com/en-us/HT209044

Make sure your carries do support e-sim, some carries may not have support it.

Thank you!

-Addison.

Read and follow the article linked above.