Respond with text - a feature, where you can reject the call and reply the caller with a pre-generated text message. Apple came up with three custom messages which can be changed by custom text. For some reason Apple decided that you cannot change the text before custom message “Can’t talk right now”. This is a problem for countries where Apple don’t support their language or people who would like fully customise their message when responding to the call.

Current list of supported iOS languages:
English (US), English (UK), Chinese (Simplified), Chinese (Traditional), French, German, Italian, Japanese, Korean, Spanish (General), Arabic, Catalan, Croatian, Czech, Danish, Dutch, Finnish, Greek, Hebrew, Hungarian, Indonesian, Malay, Norwegian (Bokmal), Polish, Portuguese (Brazil), Portuguese (Portugal), Romanian, Russian, Slovak, Swedish, Thai, Turkish, Ukrainian and Vietnamese.

The rest languages like Lithuanian, Estonian, Latvian and etc can't use this feature because responding message is divided by two languages for example: "Can't talk right now...nes esu užsiėmęs", which isn't acceptable.

This can be fixed just by removing "Can't talk right now" text or adding a possibility to customize it.