frustrated about bill

I joined AT&T last week. I previously had T-Mobile, but switched because I could get better service for the same price. Or so I was told. The lady at the AT&T store near my house told me my total bill would be under $150 a month. Just got our first bill for just under $200. I went immediately onto the AT&T website and chatted with an employee. Although he seemed friendly, he was little to no help. His one and only solution was that I have 14 days to cancel my contract. That wasn't my goal. I like my new phone, I lIke the service. Why would an employee tell me to cancel? I am very frustrated. I am a public school teacher that lives on a very tight budget. How can a company that lied to me not do anything to try to make up for their mistake? Anyone know what I could do to maybe get an additional discount on my account? I NEED to reduce my bill