You MUST send a debt validation letter to Mann Bracken. They need to provide you with the following:
How they arrived at what you owe.
Proof that they a legally allowed to collect the debt either as an owner that purchased it or as contracted by the original creditor.
Any payments you have made on the debt and when.
Proof that they are licensed to collect in your state.
A collection agency can't order you to appear in court. Only the court can and only if the original creditor sues you. Or the CA if they legally own the debt