Don't have a option of support process to choose billing instead of product support when I'm trying to create a new record type

If you can't select Billing when creating a new record type, it's likely because the billing support process isn't set up yet.

To fix this:

1. Go to Setup and search for Support Processes.
2. Create a new support process for Billing Support.

After that, you should be able to choose it when creating your record type.