Your case was dismissed. That means that the bankruptcy has not changed any of your obligations to your creditors.
When a creditor charges off a debt, that means they consider it to be unlikely that they will collect. A charge off does NOT mean that you have no obligation to repay.
Short answer: yes, you still have to repay.
Your question is a little confusing to me. If 18 payments were returned to you, that means (a) your Plan was never confirmed or (b) no allowed claims were filed. If you "defaulted" on the payments, that suggests to me that your modified Plan called for a lesser monthly payment than your original Plan and you were making the lesser payments when you should have been making the larger payments.
In any case, you have not been discharged of any debts; but, of course, you will not have to pay them unless and until they ask for their money.
I would wait and see who actually wants to collect before paying. Sometimes charged off means forgotten. However, I agree, you still owe the $.
The above is general legal and business analysis. It is not "legal advise" 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. Please visit my web site: www.avanesianlaw.com for more information about my services.
If I understand your question correctly, you started the BK process primarily to save your home from foreclosure. If your loan mod now allows you to do that, without having to be in a Chapter 13 for 3 to 5 years, then I'd celebrate. You also said your unsecured debt was only the 2 credit cards. If they have charged them off, then it is possible they won't pursue collection. As other responses have already stated however, "charged off" doesn't mean forgiven or discharged. It is simply an accounting term used by the creditor to designate accounts they feel they have little or no chance of collecting on. At some point they may dust them off and try to collect, but hopefully by then you will be in a better financial situation and be able to negotiate a settlement on one or both of the accounts, again without having to file a BK.