I think the only way around it is to upgrade to broadband. I am not certain but I think the warning is standard and used by ISP's on dial up connections after a specified time to make sure that the open line is being used and not simply forgotten.
OnePlus 5 review
ManvsMachine win UK's only Gold Design Cannes Lions award
iPad Pro 10.5in (2017) review
Comment connecter un MacBook à une TV ?