Debt collectors tend to phone you every few days and they do tend to leave messages. Depending on the size of the company, you will either get one person assigned to your case or a call centre approach where someone different will be phoning you each day, however, they are easily dealt with.
The first time they phone up, explain to them that: 'I wish to deal with this matter in writing only, and should I continue to receive calls from you or your company, then this may constitute harassment' in which case I will be forced to take further action. Thank you and good bye!
Second time they phone up:
When they ask for you, just say: 'Who is it?; hold on a minute' (as if you are just about to get that person) and then leave the phone off the hook!
They normally hold on for around 4-5 minutes, but after a while they will get the drift.
OR you may wish to try:
'Could you please hold on a minute whilst I log this call, as I believe these calls may now constitute harassment'...
OR my current favourite:
Ask them security questions, like their full name, their job title, direct number and the name of their line manager. Also inform them that the conversation may be recorded for training purposes. Most mobile phones have a sound recording function. When they ask you a security question, simply say that you do not disclose your personal details on the phone for security reasons!
Either way it's great fun! And you do not give in to their intimidation! If they feel they are intimidating you, they are far more likely to continue. I have had companies give up after three phone calls because they didn't like giving me the security information I was requesting...
Don't let them harass you- Harass them!
It's far easier and cheaper to harass and intimidate those people who do not know the truth and get them to pay up, than it is to extort money out of those who are aware of their fraud.