How to remove deleted contacts from iPhone SMS section?

Although I have deleted contacts from my contact list they still pop up as contacts to select when texting and I can't figure how to remove them

Often times this happens because you have different groups of contacts stored on your phone. You may have deleted the contact from one group and not the other. To make sure you have deleted contacts from all groups, open your Phone app --> Tap on Contacts in the middle on the bottom --> look for a button at the top left called "Groups". Tap on this and tap on "Show All Contacts". The tap "Done". Now, find the contact you want to delete and delete it. This should fix this problem.