I am having trouble checking the IMEI number on my Samsung Galaxy S4 mini with Ring Plus?

I keep inputting the number into Ring Plus' IMEI checker and I keep getting this error message:

"Hm… We couldn't locate that MEID / ESN in the database. Please double check to be sure you entered the MEID / ESN correctly."

The company says they support Galaxy phones but I will need to be able to input this number properly in order to activate my account. I really like my phone (and can't really afford a new one) and have been using it with a Verizon plan for a while now but I need to change over to a much cheaper plan. Can anyone help me?

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