Anyone else getting charged for 3G?

My husband's phone uses 4G but he keeps getting a charge for $3.00 for "using" 3G. After talking with Telus they told him that they see that his phone uses 4G but that he still gets charged for 3G because his phone is apparently too old??? My husband likes his phone and has no reason to change it. During the phone call they just tried to get him on a new phone plan. How is it allowed to charge him for using 3G when his phone uses 4G? Anyone else have this problem? How did you solve it?