ask for a supervisor and politely get their name (be very polite) explain the situation and while you were told a you got b so could they release you from the contract. She will be freindly and say no so tell her you will file an fcc complaint against them. She will laugh you off so have her cancel the service (repeat polite) when you get the bill call back and ask for a supervisor explaining once again the service requested doesnt match what you received, she will politely tell you there is nothing she can do. Write down name. time called what number etc.
File an FCC complaint (fcc doesnt regulate dsl but SBC freaks when they are served wih a complaint) chances are a bill adjustment with only the monthly due until cancelation will result.
regards,
daemon