You don't have a large agency signed up, you have an individual at a large agency. Maybe they're junior and don't have purchase authorization? Maybe they are ev

You don't have a large agency signed up, you have an individual at a large agency. Maybe they're junior and don't have purchase authorization? Maybe they are evaluating alternative products? Maybe it takes months for them to get a purchase order approved and they just needed something right away? Two consecutive trials seems fairly light in terms of abuse. If the service is useful and they start using it with more clients, it'll quickly become impossible to continue the trial abuse - they'll either sign up or go away. If your company is small enough that you notice (and get annoyed by) one user running two consecutive trials, it's small enough that you can reach out to the individual(s) involved and try to turn them into evangelists for your service inside their large agency. Or if they are knowingly abusing the service, the personal e-mail may put them off. This is how the agency I'm at discovered and ended up paying for Bitbucket, BrowserStack, Trello, Slack, DeployHQ, etc. - someone on the dev team finds a new service, passes it up to his/her tech lead, who convinces management it's worth investing in the Enterprise plan when it becomes essential to the functioning of the company.