Applied at Indeed for Unknown

I had scheduled a screening call with a recruiter from Indeed for a potential job opportunity next week. However, I received an unexpected job offer from a position I had previously interviewed for, and I plan on accepting it. Now, I need to figure out how to professionally cancel the screening call without having the recruiter's direct contact information. I'm a bit anxious about coming off as unprofessional, especially since I'll have to do this through Indeed's messaging system. Any advice on how to handle this situation would be greatly appreciated!