You have to get it in your service plan.
yes the memory stays on the phone
If the messages are saved on the memory of the phone itself, you can still view your old messages. Some carriers allow you to save your data on an internet-based cloud.
I can answer my own question whoo hoo! I put my sim card back into my old phone and deleted all the old text messages and then put it back in my new one and it was fine!
Yes you can access them again on your new phone but only if you use the same sim card again and only if the messages have been saved to the simcard. I know this as it happened me recently with my new blackberry phone
You can trade your old cell phone in, and get a discount on your new phone; but you will not get the new phone for free when you trade in the old phone.
No reason why not - the old SIM card should still work.
you
YOU DONT DELETE YOUR OLD TEXTS AND TO MAKE ROOM FOR THE NEW ONES
It really depends on what phone service you are with.
You can't unless he show you what he sent to you on his phone.
to understand old pieces of text
yes. as long as you keep the old number, you can still keep track of the person. The police can ask the phone company who it used to belong to.