Internet Latency spike evenwith ethernet cable connected to pc

Hi everyone has a problem with internet latency spike. i have been playing fps games and it keep spiking. i call up to customer service and call tech and even chat up here. they are all ignore me when they noticed the problem are currently happening for me. if you guys know the way to help this pls help me. it has been 3 months and not a single day i can use my internet with out latency spike