Where I am it's theoretically cheap to submit a claim to a small claims court if the debt is below a particular limit, but in reality it's a few hours work for someone to get the paperwork together, send it in, answer the bogus rebuttal you'll inevitably get, then have someone spend half a day at the court waiting for a hearing, getting an enforcement order, then having them still refuse to pay over a few hundred dollars of unpaid phone bill.

For most places it's easier and cheaper to just cancel your service, blacklist you, register the debt with a credit rating agency and hand it over to a debt collector