Ideas for conveying credibility of service to customers?

If your own confidence is high, then offer some kind of satisfaction guarantee or perhaps a trial license. (wait, I think you already do this) There are three elements of persuasion. 1) personal benefit, 2) dramatic difference, 3) reason to believe. Number three is usually the easiest for most companies. Number two is the hardest for most companies.

I appreciate that you listen to customer feedback, because one vocalization usually represents ten that never say anything. But, don't let it get you down. Perhaps this customer simply isn't a trusting person.

Maybe look at it from his perspective, not that it's your credibility at stake, but whatever FOMO issue he is having. What will he lose if you can't do what you promise? You won't please everyone. You don't have to win or keep every customer. Have you asked this person what articles the other service is delivering that you are not?

A straightforward answer is to have other customers validate your service directly. If you solve customers' pain points, other customers will be more likely to follow, even thought no two issues are 100% identical. If you have too few customers/clients do do this, you need to acquire more.

Thanks, Paul and George! It's very hard for other customers to validate perfectly because we track a LOT of journals. So if someone doubts whether we are finding all the articles, it's very difficult to check.

@ Mayank Ved note that net promoter score (NPS) is still popular, but conveys extremely limited information. General wisdom in Marketing is that NPS precision is inadequate to give enough information to implement change, and mostly a waste of time compared to other possible testing mechanisms. Also remember that consumers are more likely to say no to something that they don't understand.

@ Mayank Ved I generally like HubSpot, until they're annoying, but even they say that without the conversation that NPS inspires, it is useless by itself.

An unmodified "Net Promoter" method of measuring customer satisfaction ranked last in an extensive study by Schneider et al. in terms of predictive capability.

Good NPS scores correlate to customer loyalty

and that's all. (Forbes)

Likelihood of recommending is not the same as will recommend. (SmartCompany)

Kill the cockroach of a management metric, the NPS score. (The Financial Brand)

NPS considered harmful and what UX professionals can do about it. (Medium)

NPS doesn't allow for incremental improvements, and people just don't make recommendations about a lot of things.

Major reasons why your NPS implementation is almost useless.

Outliers that are looking for something really impossible are tough to satisfy and entrepreneurs have to be okay with not being able to (or risk spending too much time on outliers). For everyone else, case studies and limited trials works great.