How to activate my iPhone 3g?

I was cleaning out the spare room and I found this iPhone 3g, brand new and barely used. Apparently this phone belonged to my aunt and she didnt know how to activate it so she gave it to my mum to activate it but she forgot about it. I asked my auntie and she said she didnt want it seeing as she has the new version.

Now I'm really confused, how do I activate it? I put my sim from my old android into it and stuck it in itunes but it said "the SIM card inserted in this iphone doesnt appear to be supported" What do I do? I dont really want to shell out $70 for a phone plan when I wouldnt even use it much…

My mum has an iPhone 5. Could I use her sim to activate it and once its activated could i use my sim?

Thanks for reading it all. I hope to get an answer soon

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