Whatsapp Verification with SMSPva

How does that work exactly? How can I verify Whatsapp with their service?

I always thought that you need a sim card that you put into your mobile phone. Then whatsapp needs to verify the very same number.

How can I verify with Smspva when the number that I get from there doesn't match the number from the sim card I am using?

Is it possible to get whatsapp without a new sim card? Can I use smspva to emulate different phone numbers for whatsapp even when still using my old sim card??

Thanks