In order to help Contacts manage their Subscriptions, sometimes it's necessary to guide them through their Subscription Pages and Subscriptions. To do this, navigate to the Contact page in Salesforce and click the Subscriptions button in the top right section of the Contact. (The button may be hidden within the carrot menu). 

You'll be taken to the Contact's Subscription Pages, all summed up on one screen. Please note, you can not opt Contacts back into Campaigns if they have globally opted out. You will still need to contact the CRM team for assistance. However, you are able to manage individual Contact's subscriptions from this page.