Why are the people in cellphone stores such scumbags?

Yesterday I took my backup phone to AT&T to try their service and get signed up for the 55+ plan for $40/month. Today I check my acct and the MFer signed me up for the most expensive plan at $96/month. I just got off the phone with CS and they can't change it for 14 days, but she noted the "mistake" and says that I should call back and confirm the proper change and credit.