Final answer:
If Janis receives a credit card bill for a guitar she returned to the store, she can dispute the charge by providing proof of the return. The credit card company should investigate and adjust her bill.
Step-by-step explanation:
If Janis received a $3,000 credit card bill for a guitar she returned to the store, she should contact her credit card company to dispute the charge. She can provide proof of the return, such as a receipt or tracking number, to show that she should not be responsible for the charge. The credit card company should investigate the situation and adjust her bill accordingly.