A credit card can help your credit score improve if you pay it on time. Over time it will show you have a good payment history and it can also diversify your credit if you have other types of credit...
Companies that offer credit debt relief services, actually approach your creditors in order to negotiate and reduce the amount you owe. It is also possible to negotiate for lower rates of interest...
Truecredit does not necessarily help rebuild credit. Truecredit is a website that stores credit histories. You would visit truecredit to learn your credit score.