MX Energy False information from salesman and early cancellation fee not in contract. Internet, Texas

I was contacted by a door-to-door salesman/representative and told that I was going to have to choose an energy supplier separate from PSE&G in New Jersey.  I was also told that my bills would be significantly lower if I chose MXEnergy.  I thought the information seemed reasonable; I had heard that alternate energy companies would be contacting us although I had not realized it would be necessary to change. I signed the contract. I did not read the entire page as is usually my habit.  In fact, if I had read the entire page of the contract I'd have found that choosing an alternate supplier was not necessary.  If I had read that, I'd have realized the salesman/representative was lying to me and I would not have signed.  Anyway, since I did sign, I was stuck with the contract.  I paid all of my bills. I had had PSE&G on auto-pay but when shortly after that they took out a small payment on a day other than the usual day, I stopped the auto-pay and responded only to bills sent through the mail.  After approximately a year, I was getting married and moving. I sold my home. I read the contract I had signed and it said that if I moved and closed the account with my primary energy supplier, PSE&G, that the contract was ended. There was no mention of an early termination fee or paying for energy already purchased for my account.  So I was surprised when a letter from MXEnergy was forwarded to my new address in a different state telling me that they had purchased $150 of energy for me that I must pay for.  I wrote a letter back but did not send it because my printer wasn't working.  Now I have received a letter telling me I owe an early termination fee of $150 and if I do not pay, they "may" have to turn my account over to a collection agency and they "may" have to notify credit rating agencies of my nonpayment.  From what I have read, I feel sure that they will turn the account over to a collection agency and try to impact my credit.  I don't understand how they can do this when it is outside of the terms of the contract.  I may sue.