iPhone uses iMessage, not "text" (SMS). If the sender ever sent you a text on an iPhone of yours, they have to mark a text to you as SMS, otherwise their phone will continuw to try sending you an iMessage (which you'll never receive). It's a good idea for them to do that at least once anyway, in case their phone defaulted to iMessage.
Recently, however, it appears (you'll never hear it from Apple) that Apple has been having problems with iMessage (emojis causing entire texts to appear in Chinese, etc.), so if tagging a message as SMS doesn't fix it immediately, wait at least a few days.
10-30-2016 12:53 PM
