I'm sorry that you had this poor experience. I think while the answers may have probably been factually correct, at the end of the day it's our job to explain the situation in a way that empowers you and sets your mind at ease.
Shaping at the moment is applied based on demand. During the day we shape all users from about 7:30am to 10pm, and thereafter we dynamically shape according the demand on the network. We don't shape based on a threshold or usage total, so whether you have not used your account for some time or not, shaping could still be applied after peak, and will definitely be applied during the peak day period.