Gifts from customers during the holidays are one thing that rises to reasonable exception, but, buying and/or picking up products and transporting it by UPS TRUCK and not paying for the shipping is strictly against UPS policy which is posted in every center. Every commercial package picked up or delivered has to be paid for. You can not use a UPS truck and/or UPS employee working time to engage in personal business that is not directly related to your work duties.
Do not talk to customers about you personal issues regarding repairs, products, or service on UPS time. Do not transport personal property ( your lunch box doesn't count) using a UPS truck. When you are on the clock and in command of a UPS vehicle you are to be doing what the company is paying you to do and nothing else. Its that simple.
Hope they can strike a deal and reinstate you. I'd start "getting it" and stop the denials.