Cloudflare's Optus issue

Hi,
My SEO team said that if I set up Cloudflare proxy for my website, Optus internet users (only) in Australia will experience slow speed when exploring the website. How can we fix this issue?
Thanks.

Did they explain why Optus internet users in Australia will experience slow speed when exploring the website?

If it’s because of peering issue, some regions/ISP have high cost of peering. Some of the telco providers are exorbitantly expensive. As a result we may choose to only provide / advertise particular ranges in certain peering scenarios and this may mean that for certain plan types peering may be to a datacenter elsewhere in APAC. The broadest coverage/peering would be available to Business and Enterprise plans.

We encourage our end-users to reach out to them and encourage them to become our ISP. You can read more at https://blog.cloudflare.com/bandwidth-costs-around-the-world/.