Instruction to reset password by June 26. Is this a scam? Why necessary?

djvr wrote:

It came as a message on my iPhone, repeatedly

If it came as an MSM and your device does not have profile (or company owned) like Demo said, then I would say that it is a scam. I would delete the message without clicking on any links (again see Demo's advice which is good).

Then it is likely a scam. So take elcpu’s advice and delete the text and don’t click on any links.

It is very likely a scam. Do you reply or click on links.

Where did you see this message?

Is your device company owned? Or does it have some sort of profile on it? Some company owned/controlled devices may require password changes every so often on a regular basis.