We are planning to create series of consistent advertisement messages but we found ads ideas that tap into customer desire are the most difficult part. Is there any tool or agencies that can do this brainstorming for ads ideas?
Sure, there are all kinds of agencies you can hire. But outsourcing won't help if you're unsure what you're looking for. You say that your biggest difficulty has been to tap into the customer desire. Is that because you're unsure what the customer desires are, or because you don't know what kind of campaign would engage people with those desires? The first would require a market research specialist; the second would require a messaging specialist. While some agencies do both, they're not the same thing.
No matter who does it, the most important thing (well, depending on the product) is to focus your messaging on benefits, not features. Let's say you sell a service that helps businesses identify all laws/regulations that pertain to their business, determines whether they're compliant, and, if they're not, guides them through what they need to do to get there.
Those are the features. The benefit is that the business owner can sleep at night instead of worrying about losing the business due to a regulatory violation. So, in that case, your messaging might focus on sharing fun, relaxing times with friends and family instead of lying in bed, wide awake, and staring at the ceiling.