i bought an iphone today that says its lost with a phone number but i cant get into contact with owner

You have encountered Activation Lock. Without the apple ID and Password of the original owner, you will never be able to use this phone. Check this link...

The All Too Common SAD Reality of Buying … - Apple Community

You can recycle the device at any Apple store.

Return the phone for a refund immediately. The phone is totally useless unless the original owner removes the activation lock. And.....if you can reach them.....they will probably be unwilling to help and want the phone back since they have reported it lost.

Don't buy a used phone.

Congratulations, you have most likely bought a stolen device.

Turn it into the police.