If you've just migrated your contacts from
iPhone to your HTC phone, your contacts may still be texting you through
iMessage service and not through SMS or MMS.
To receive their text messages on your HTC phone, you must turn off the
iMessage service in your
iPhone settings. If you have other
Apple devices, you also need to turn off
iMessage on them.
Or, go to your
Apple support profile on the web and unregister your
iPhone and other
Apple devices.