If Midland Funding has three debts, the fact that you know this means that they know this, too. If they have sent you what is called a "dunning letter," a letter asking you to pay the debt, then you should send them a validation request. For now, my opinion is to wait until then to do this.
As far as how to handle Midland Funding, do some Google research on them. You will find tons of material to use. Use the phrase "Midland Funding adverse court actions."