What happens if i try to use the phone while the lines are being cleaned?

I got a call today saying that from 5PM to 11 PM that there would be a cleaning of the telephone lines. I was told to put a bag over all telephones to remind people not to use them during the cleaning.

I was also told that I should disconnect all computers from the internet during the cleaning if they are connected via dial up.

They said this cleaning was being done by AOL to remove abandoned websites and to speed up services. What happens if I use the phone during the cleaning.