United Collection Bureau Debt Collection Harassment

I keep getting calls from United Collection Bureau about a debt I do not recognize. They call early in the morning and late at night, and they have left voicemails that never say they are a debt collector. A few times they called my family members and talked about the account, which was embarrassing. I asked for proof of the debt in writing and nothing ever came. Now I am worried they will try to sue me even though I have no idea if this debt is even mine. Has anyone else gone through this with them?https://protectionforconsumers.com/united-collection-bureau-debt-collection-harassment/