How do I remove unwanted Calendar events on my iPhone?

Can anyone tell me what this means please? I got a new phone about 8 years ago and when I was in the store swapping my old phone over to the new one something was installed onto my calendar.

The man who worked in the store done the swap over for me and ever since then I’ve had this Chinese event put into my calendar and it read this DECLINED: Sands Singapore (41700700.com),...

05:46.

Its on every single day of the calendar.

I’ve had numerous phones since this particular one mentioned above and this has copied through to every calendar?

Has my phone been hacked? How do I get rid of this?

[Re-Titled by Moderator]