Nobody likes when a debt collector calls to ask about an over due student loan payment, medical bill or an unpaid credit card but avoiding these calls is not the right way to go about dealing with this debt. Not answering the phone is a bad idea and can only make matters worse. The best way to to deal with debt collectors is to not let your debt go to collecting in the first place.
This means you must work out an arrangement before your debt goes to collection and you also want to educate yourself on your rights so you know harassing phone calls and threats are illegal. Before those calls started, you had already received letters about your debt so the phone call is the next course of action to collect. If you receive a notice about a debt that is not yours, do your part to protect yourself by contacting the debt collector and letting them know there has been a mistake made.