Before you approve the mockup
Nothing has been printed yet. You can change the design, the count, the sizes or the date, or call the whole thing off. This is the easiest point to change your mind, so speak up here.
After you approve
Approval is the point of no return. That is not a technicality. Screens get burned for your design.
Blanks get pulled for your count. Both are specific to your job. Neither one can be sold to somebody else.
If the printing is wrong
The shop stands behind its work. If the print came out wrong, or a garment showed up defective, call the shop. Bring the shirts back and it gets made right.
Do not wash them first, because that makes it much harder to tell what happened.
If the mistake was in the file you approved
A misspelled name on the mockup you approved gets printed that way. That is why the approval step exists. A reprint in that case is a new order. The shop tells you what it costs first.
Deposits and payment terms
The shop confirms deposit and payment terms on your quote. That happens before printing starts. Ask about it when you get your number.
Cash App is accepted. That helps when one person is collecting money from a group.