One of the cardinal rules of contracts is that words are given their ordinary plain meaning. This rule is applied within the context of the transaction. If words have a usual or customary meaning within a particular industry, then that meaning is attributed to the word used. If you want to depart from that rule, you have to provide a definition in the contract.
Hard drive manufacturers got into trouble with this principle when they quietly redefined a megabyte to be equal to 1,000,000 bytes instead of 2^20 bytes like everyone was used to.
If I had AT&T as my service provider, I would be complaining to the Federal Trade Commission alleging this as a violation of Section 5 of the FTC Act. I would also be complaining to my state's Attorney General alleging a violation of my state's consumer protection laws.