Postal Annex Outrageous Purchase Policies, payment policies not clearly posted, extreme price mark-ups Oceanside, California

I went to mail a camera battery. It is about the size of a credit card.. I took an envelope from their shelf ($1.30) and filled it out at the counter with the lady who works there. She then told me it is around $4.30 total to mail it. I took out a credit card and an ATM card. and she told me that I could only use a card if I spent a minimum of $7.00. She then took a hold of the package with my battery and said she will hold it until I pay for the envelope. She told me to go next door and buy something and bring back the money. I was being extorted. There needs to be a sign saying they have a $7.00 minimum with an atm or credit card. I will never go to another Postal Annex with such abusive policies.