installation fee

Hi, my bill recently went up and i see that the 1Gbps option is now cheaper than the 400Mbps plan i'm on so i was going to switch, but i see there is a $100 professional installation fee. Is this fee necessary if i'm just switching plans? I see it listed on the 500Mbps and 300Mbps plans as well. What would need to be installed? I own my router and modem. Would this require a technician to come to my house? If so, what would they be doing?