Changing an SSN is complicated, you would have to apply at the Social Security Administration.
If you want an IRS way to stop them from being claimed, you can file a form 14039-T for identity theft. If the IRS accepts the form, they will issue an Identity Protection PIN code for your dependents, and a tax return can't be e-filed without it. The IP Pin changes every year and is mailed to you in December.
If you are having a problem this year, print your return and mail it in. Don't change your dependents if you are allowed to claim them. The IRS will investigate and figure it out.
