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Allied Interstate is a collection agency. Next time, you should ask them why are they are calling you again and again? If it is regarding a debt, then ask them to prove that you owe it. You can send a debt validation letter to them via certified mail. If they are not able to validate the debt, then send a cease and desist letter to them. You can get more information on allied interstate from the following page:
If you really owe the debt, then you can negotiate a payment plan with the collection agency. You can also contact a professional debt relief company if you're not able to reach an agreement with the CA. The debt relief company will help you pay off the debt.