Internet usage

I’ve had internet with since April 2023 and We never went over usage. Come May 2024 we are going over every month. Which doesn’t make any sense. With my daughter working and it being summer we were out of  the house and there is no way we went over .I’ve spoke with customer services, online and over the phone several times. They keep telling me to change my password and a name which I’ve have several times. Also suggested I upgrade.I explained to them maybe they should find the problem and fix it first. They haven’t found the problem and I refuse to upgrade when I know nothing in my household has changed. I ask could they send someone out to check the lines and they want me to pay for the service fee. I will be searching for other services. I rather pay more for a honest decent service.