so this just started when you got the 2.4 router. our is it just cross talk with an ac line next to the phone line.
what you do as a troubleshooting tactic turn your router off. Use the phone call a family member. Just good points. If there is no static. Your good. Buy the new phone. If there still is static while talking to the family member ask them to come and bite your foot buttttt still thank them for the conversation.