Text Messages missing after Restore from Backup

Hi,

I purchased a new Iphone 6s (came from 5s) when it came out but had some heating issues.

Yesterday I went to the apple store and got the phone replaced (new one).

I chose the backup I did the night before (automatic backup) and in a few hours, it was done.

Everything came back expect for text messages.

This morning, checked and still nothing. So i did the restore from backup again and choose a backup from a few days ago.

Same thing. Everything came back but all my texts from the last few years are gone.

Please help.