Internet problem

We have been suffering from an unstable internet connection at office. It occurs intermittently, gets worse on the bad weather day or after a storm. Today, we had an insistent problem from morning. We have already checked our server, modems, spliter, lines and other peripherals, talked to Bell Canada and ISP. Recently, it was working much better than the last year, but today's situation was fatal. We couldn't hook up to the internet, fax line was killed, also we couldn't use one of the external phone lines. Called ISP first, they said they didn't have any problems. Then we called Bell to ask them to check our lines. Around 3 o'clock, the Bell guy came to the office. Finally, he reinstalled our lines to the new transmitter box outside.