Doesn't seem too confusing. Op, were your 'old' phones more than a year old?
"if we kept our old phones we'd only be charged $15/mo for line access. We decided to go with this option temporarily as we were waiting for some of the new phones coming out."
It is because then they say
"When we contacted customer service about this, we were told by 2 reps our only option was to return our equipment and go elsewhere"
Which makes it seem like they got new phones already. If they were still using old phones not on contract all they have to do is go on My Verizon and activate the Month2Month discount.