Can I add another iPhone after erasing my old iPhone?

Can I add another iphone after erasing my old iphone

After dropping my old iphone down the toilet which has left it unusable, I have bought a refurbished iphone 6s. But when I switch the iphone on I come to the part of 'Requesting a Activation code'. problem is I am not receiving the code ( Not sure if it is going to the old phone) But I am still using the same Sim card

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