Refund

We did a payment for bonnet and the left door mirror. They said we're going to get these parts but only to find out they are unable to get them. Now the problem is they don't want to refund us the money in order to buy these parts somewhere. They want to sign a document, which states that there will be a deduction of 20% and we will get our money after they have done an investigation within 14 days. We want our money back from this company. Thank you