Hi @Hirwa,
Welcome to our Q&A forum!
We are having issues with our on-premises exchange server.
What is the specific issue with your on-premises Exchange server? The Q&A forum may be able to provide some help through forum discussion.
If you prefer phone support, we recommend that you open a phone support ticket using the contact information provided on this page https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
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