Depending on the time since the last default, part may be barred by the statute of limitations of 4 years. If the business debts were in the name of a business entity, they may not be your personal debts to pay. Good luck.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
My colleague is correct. One thing, however, most business credit cards are based on your personal credit and that means the suit to collect would be against you personally. Large companies have credit cards based purely on the business credit, but for most small businesses what you have is a credit card based on your personal credit with the name of your business.
Good luck and speak with a local attorney if you are sued to see about possible defenses. This is critical.
This answer is for informational purposes only and is not legal advice regarding your question and does not establish an attorney-client relationship.
I edited the practice area so you can hear from some debt collection lawyers.
You should write the collection agency asking them to "validate" the debt. They need to clarify if the debt is your personal debt, i.e. whether you contractually agreed to be liable for the debt of the business. (I am assuming the business was a corporation.) If your business was a sole proprietorship or a partnership, you may already be personally liable.