Can a "2Wire 3801HGV" modem/router be replaced with a "PACE DSL Gateway Model 4111N" modem/router?

I asked a question before agreeing to sign up with AT&T regarding the
equipment fee --

I was told by the sales rep over the phone that the fee was like a rental
fee for using the equipment, so I asked, if I was to buy my own
router/modem would the fee be cancelled and she said yes.

Are you telling me that I was lied to by an AT&T representative who was
willing to tell me anything to get me to sign up (an act that is considered
illegal)?

Will you please explain to me what the charge is for if not for the
equipment...and if I can buy my own equipment (a 3801hgv) in what way AT&T
justify charging that fee if I was no longer using their router/modem but
instead using my own identical router/modem?

I sincerely appreciate you taking your unpaid personal time to answer
questions. Thanks.
I will contact the Better Business Bureau and the FCC regarding the illegal
marketing and sales tactics used by AT&T in hooking customers. You are
correct about being subject to terms that are agreed upon but if the terms
are conflicting with what is being promised in marketing then it's a
violation.