Great questions. There are many things that you can do, not only to help your mother but also to help you.
1. Collect detailed information on EVERY call. Date. Time. Number called from. Caller's name. Debt collector's reference number for account. Kill them with kindness and get information.
2. Send them a cease and desist letter certified mail return receipt requested. Reference the debt collector's internal reference / account number. Ask them to stop contacting you about this debt. If they are calling your call phone, also tell them they do not have the right to call you there anymore.
3. Have your mother also send a cease and desist letter telling the debt collector to not contact her any more.
4. Then sit back and wait. If they call you or your mother again to collect the debt (or write a letter trying to do the same) get the letter, go to an attorney and you can file a lawsuit for unlawful debt collection. YOu may be entitled to up to $1,000.00 damages, the calls will stop and the offending debt collector must pay your attorney's fees and costs.
If you have voicemails now and they fail to properly identify themselves, YOU may have your own case right now. While I am not licensed to practice law in MT, the Fair Debt Collection Practices Act is a federal law that applies in all states. Feel free to visit our website if you have any further questions. www.ConsumerRightsGroup.com Good luck!