If you're using Okta Verify push to the device for your MFA then the push will not reach your device, since it's now effectively a new phone. You can take steps to un-enrol your old phone and then set up the "new" one (https://help.okta.com/en/prod/Content/Topics/Mobile/okta-verify-enroll-new-device-existing-users.htm) but this will be a pain, as you'll have to undo it when you come back.

But if the same Okta Verify app is running on the same device overseas, even with a different SIM and number, the one-time passwords (OTPs) it generates will still be valid, so you could ignore the push attempt (if any) and use that OTP code to MFA each time. I just tried this by removing the SIM from my phone entirely (and turning wifi off, for good measure) and I was able to MFA into my Okta instance using the OTP that the app running on my phone will still generate. You could do this overseas and then just revert to using the push when you come back.