I have been successful for another Master’s programme and have to decide whether to accept or reject the admission. What should I do?

Universities often allow you to exmatriculate after a short period of time following enrolment; in most cases, you will also receive a partial or full refund of the fees.

So enrol for the other Master’s programme. As soon as you receive an admission letter for the Master’s in Statistics, exmatriculate for the other Master’s programme and enrol yourself for the Master’s in Statistics.