State Bank Of India [SBI] — It's been a month and i haven't received my refund from walnut app

Address: Pune, Maharashtra, 411067

Website: www.walnut.com

I've made transfer of 2500rs using 'walnut app' but the amount got debited and didn't get credited into my sons account, and the company has provided me ARN no: 85215227165723480190494 to track refund status and i've repeatedly visited my bank and the manager says that the messages are spam messages and there's no such arn number that gives details about the refund.
name: md jaweed pasha
sbh acc no: [protected]
branch: sbh dubba nizambad
mob no: [protected]