At an elementary level, this includes the refusal to answer one's phone by screening one's calls or by ignoring mailed notices informing the debtor of the debt.
Some countries limit the use of imprisonment of people who are in debt as a method of forcing their repayment.
They are usually employed by large companies, so the likelihood the same agent will talk to the same debtor within a short enough period of time is low.
Many attempt to avoid contact with the sheriff and pretend they never received the summons.
Once the limitation period expires, debtors can use this fact to stop the calls from an agency by demanding a civil suit be initiated, at which point they may successfully defend based on the expiration of the limitation period.