Download speed is not as advertised

I signed up with Xfinity understanding that we had an agreement that i would get roughly or close ~1gigabit per sec download speeds but after continuously and rigorously checking the speed I'm averaging 300 Mbs ~ 500 Mbs. Mind you I am testing on a 2025 Asus ROG Strix Scar 18" 2025 model, monster of a gaming laptop, with a literal modem proximity of less than 15 feet. This is unacceptable and grounds for false advertising. Please reach out to me and correct this matter or I will be forced to file civil charges against your company.