My question related to message announcing to my phone with calendar alerts

Hello atef261,

Thank you for using Apple Support Communities! I understand from the information you provided that you’re subscribed to calendar that you do not want to receive notices from; I'd like to help.

The following support article provides some steps for unsubscribing to calendar:

Use iCloud calendar subscriptions - Apple Support

If you have recently installed an app that also install a configuration profile on your device, this article shows how to deleted the app and profile:

How to delete an app that has a configuration profile on your iPhone, iPad, or iPod touch - Apple Support

Hope this helps.

Best Regards.

Probably you have accepted an offer or subscribed for a spam Calendar accidentally. Watch the GIF below to unsubscribe