Existing customer looking to move to the national 1 Gbps $50/mo 5-Year Price Guarantee

I have been an Xfinity customer for over 6 years and am currently paying $55 for 500 Mbps having come off a $50 for 1GB deal for 5 years. I see the national promotional tier is offering 1 Gbps for $50 on a 5-year price lock. I want to transition my account to this rate immediately to avoid canceling my service for Verizon Fios. Can this be done? Thanks