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If the debt is yours, you can usually expect they can validate. Not always, but usually.
What you gain in sending a DV is that they must cease collection activity, including reporting to a CRA, until they provide the requested validation.
It might gain you a temporary respit from their reporting, but they need only validate, and can then immediately report.
They dont have to prove the validity of the debt, they are only required to investigate and make a determination that they have obtained adequate information to verify.
Untilt they choose to provide the requested debt validation, if your DV is timely, you cannot negotiate any terms of payment with them untilt they have first provided validation.
You will get differing advice, as there is no yes of no answer.