Under PSD2 this is illegal - sadly the implementation date is in Sep 2019. Appalling treatment and Revoult has been getting some bad press recently - you should complain to Financial Ombudsman - https://financial-ombudsman.org.uk (assuming you are dealing with Revolut UK, and they have not switched to Revolut Payments UAB for EU customers)
I already filed a complaint with them, but apparently Revolut can just refuse to reply and that's that. They also told me as much, they said I have to file a formal complaint with them first. They said something like "we will refuse to process any other complaint until the formal complaint process is complete", but since they're judge, jury and executioner on this, I don't have much faith.
Revolut can't refuse to reply. They are literally advising you on the first step to file your complaint in this procedure, as prescribed by the Financial Ombudsman Service. It is there to exhaust your query, in order to either resolve the matter amicably or to arrive at some satisfactory conclusion and more importantly it exists to filter out any frivolous claims.