WI-FI modem downgrade

Initially I was provided with 5.0 2.4 Gig Modem new standard after I got accustomed to that modem Comcast recalled it and replaced it with a dual modem of 2.4 ,2.4  They never replaced my modem with the original speed that they had provided me initally,   I'm very dissapointed with  Comcast for doing somthing so underhaded. I have attempted to get answeres to no avail.