lost 5g

my home internet gateway was losing signal and cutting out intermittently. I called customer service and they stated they had lots of similar complaints in western north Carolina since the hurricane ( Helene) had knocked out all their services for many weeks. since resuming services many customers needed to replace the gateway devices. they sent me an exchange gateway and I set it up to replace the old one and returned the old one… NOW I find the replacement gateway is causing my streaming and my laptop to all slow down and buffer too much. when I press button on gateway to check signal it shows 4 bars and says I have a good connection BUT it shows a 4g signal…. I seemed to have lost my stronger and faster 5g connection.. how can I get back a 5g service????? I am still paying for unlimited 5g home internet but only getting 4g part time service!!!!!!