How do I unlink my iPhone from my husbands iPhone?

It sounds like you may be sharing an Apple ID which is never a good idea. Apple IDs were never designed to be shared.

If it turns out you two are indeed sharing an Apple ID, one of you will have to sign out of your iPhone, create a new Apple ID account, and sign back in.

To sign out, go to Settings > [your name] > Sign Out

See here for more information: Make sure that each family member has a unique Apple ID - Apple Support

In addition to void_ranger9's excellent information, you might want to review this user tip:

How to “unshare” an Apple ID - Apple Community