Why can't I delete auto backup photos?

OK this is going to be long bit stick with me. I have a galaxy note 2. I have Google+. I have the auto backup feature disabled. HOWEVER, it appears that when I last switched phones all of my old photos that had been backed up are now on my new one. I wasn't aware they were being saved. Now these photos only appear in my gallery. I can't find them anywhere on google+ or photos. The gallery doesn't give me the option to delete them. I'm at a complete loss. I have no idea where these photos are, how they got onto this phone, or how to get rid of them. I am on straight talk. When I switched to my new phone (which is from at&t though I still have straight talk service) I purchased a new sim and transferred my number. Have no idea of this matters but if anyone can help that'd be great. I can't find anything online and I have searched.

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