iOS 14.7: Respond with Text SMS FAILS- with an incoming phone call from a new caller to whom SMS has not been sent earlier after a reset of settings on a dual sim iPhone.
This issue is regarding dual sim iPhones.
If sending SMS message is attempted from incoming phone call screen by the option of using “Respond with Text”, the SMS sending fails if an SMS has not been sent earlier to that caller from the iPhone after a reset has been done of its settings. This happens irrespective of the receiving phone line is setup as the default Data line, default Phone Calls line, or default for both Data and Phone calls, or default line for none.
The SMS text message using “Respond with Text” option gets sent and delivered to that caller only if that caller has been sent an SMS message from the iPhone earlier.
Further, if an SMS is subsequently attempted to be sent to that caller (after SMS sending fails while using Respond with Text options), a prompt (“Number not available. Which number would you like to send the message with”) appears in messages app asking to select one out of two phone lines to be used - out of two mobile phone lines of dual SIM iPhone, which has to be selected before any SMS message gets sent from using “Respond with Text” options on incoming phone call screen.
This confirms that the phone line of the incoming call is not getting utilised automatically at the back end of Phone app/ Messages app for sending SMS through “Respond with Text”. Neither is the default phone line configured for calls or data getting used. This unexpected behaviour persists until atleast one sms is sent to the caller on messages app from that iPhone prior to receiving the incoming call (but after a reset of the iPhone settings).