What to do to extend the warranty

If you purchased the one time payment option for Apple Care+, in 2019, you can now extend it as a monthly payment option, indefinitely.

See here: About continuing your AppleCare+ coverage for iPhone, iPad, and Apple Watch - Apple Support

Can I switch to a monthly plan?

If you paid upfront, you can switch to a monthly plan when the 24 or 36 month period is over.

When my 24 or 36 months of coverage ends, how do I renew coverage on a monthly basis?

Renew your coverage at mysupport.apple.com. You can renew your coverage within 60 days of the end date of your original coverage.

chand273 wrote:

my phone coverage warrenty expire 28 may 2020

That means you originally purchased the phone 28 May 2019. You would have had until 28 July 2019 to extend the warranty. Since we are long past that, you can no longer extend the warranty through Apple.

You have 60 days from the original date of sale of the device to purchase AppleCare+ coverage.

Thanks, Phil. I still forget about the monthly option.

IdrisSeabright wrote:

Thanks, Phil. I still forget about the monthly option.

No problem.