They keep ringing with "No Caller ID" about 5 time...

They keep ringing with "No Caller ID" about 5 times a day, over the last 8 weeks, chasing up an Eastlink debt of $7.00.....really???? I refuse to answer No Caller ID calls, but finally had enough tonight (yes, ringing at dinner time is a nuisance too) and couldn't believe the harassment over a debt under $10!!