You do not indicate in your question why Comcast is contacting you. However, if it is because you are past due on your account, the company can contact you at work. If an outside debt collector were contacting you about the debt, the federal Fair Debt Collection Practices Act gives you the right to tell the collector not to call you at your place of employment assuming your employer does not want you receiving calls from collectors on the job. However, the law does not apply to companies that are trying to collect their own debts.