Resolve Wired & Wireless Connectivity Issues

Both our wired LAN and our Wi-Fi network are intermittently dropping or slowing down, and routine fixes have stopped working. I already handle basic updates and monitoring, so what I need now is focused network maintenance that zeroes in on troubleshooting these connectivity issues... (Budget: $15 - $25 USD, Jobs: Cisco, Firewall, Network Administration, Network Engineering, Network Security, System Admin, Troubleshooting, Wireless)