Software update
How can I update my iPhone 6plus if it doesn’t have software update option
How can I update my iPhone 6plus if it doesn’t have software update option
An iPhone 6 Plus cannot update past iOS 12.5.5. You need a new phone.
An iPhone 6 Plus cannot update past iOS 12.5.5. You need a new phone.
See if this helps: If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support
and contact your carrier for help with this.
What about sending sms??they are not delivered
Software update