Chase is notorious for this...I have 3 friends who are banned because of the same situation. Even though they have changed banks they have not yet gotten their accounts back because they got beligerant and verbally abusive the first time arround, which makes everything more difficult.
If you really want it back...Go into the bank itself and ask for a customer service manager, bypass the tellers. In as few words as possible, describe this situation, and on a paper list the actions you have already taken. If you have dates all the better. Since the glitch happened with them, insist they call SE (or was it POL) to fix the problem, in your presence. If you decide to change banks try getting help through the new bank.
SE customer service sucks majorly. You are going to have to be direct, but polite, with the reps. When they ask "How can I help you?" Tell them you need to be "warm transferred"(they have to hold with you until the supervisor answers) to a supervisor. Make sure you get a direct number to that department before you are transfered. They are going to try to insist that you have to deal with them first but be insistant in that you already know they can't help you and to just be transferred.
Breifly explain what you are trying to do and ask for advice on how to get your account unbanned. Do not argue with them, don't threaten, try not to raise your voice, it will decrease your chances of getting help. If NO luck ask for a department manager, if still no luck ask if they have a customer retention department, or someone who can help you resolve this problem that is not of your creation. There has to be a contact somewhere within the company that will be able to reverse this.
Make sure you keep a journal of your progress, names/rep ID's and phone numbers. If nothing else it might be useful for other ppl who are in the same situation.
Good luck