Two text threads for the same phone number

[MeganJane]

I'm so frustrated with texts on my Galaxy S7. I send a text to someone in my phone book and receive the response in a new text! These aren't MMS, but just general texts.
How can I merge the two threads?

 

[anon(19759)]

Are you using a third party text app?

 

[MeganJane]

Nope, the one that came with the phone.

What happens is that the text appears as a new number incorporating #61 in front - Australian code.

 

[MeganJane]

Surely there's an answer to this!! I transferred all my contacts from my iPhone 5C. Everytime I text a person, there response is in a different message - always with +61 in front. Even if I change my address book to include the +61, it's still a new message!!

 

[1812dave]

Ask your carrier.