Problems with company that triple charged account never shipped item caused overdraf fees etc...?

I ordered a Pda and some programs that I am required to have by a certain date at my school. The programs have to come from this company and the pda has to be compatible with their programs. Their website messed up and charged me multiple times, it took me over a week, several phone calls, emails, online chats, and my bank statement to get them to remove the extra charges during this time I incurred $124 in overdraft fees at my bank due to this. They ignore my messages about the overdraft. I have sent them another email because I never received my pda and now they say they forgot to ship it and it is now out of stock. But I can upgrade for a huge charge. How can I get them to either pay me the money for the overdraft fees due to the erroneous charges or upgrade me for free or both since all of these things are errors on their part.