Yes. Acas conciliators must carry on trying to settle your claim until it is withdrawn or dismissed by the tribunal. Usually Acas will try and arrange for the same conciliator to be assigned to your claim all the way through. Acas conciliation is free.
When the ET3 defence form is sent to the tribunal by the employer, a copy will be sent to Acas, who will offer you and the employer conciliation to try and settle the claim out of court. You are under no obligation to accept conciliation, but assistance from Acas can be useful at all stages of the employment tribunal.
If you agree to Acas conciliating, it may reach a formal agreement between you and the employer, known as a COT 3. Acas does not charge for its conciliation services. By agreeing the terms of a COT 3, you accept a stated sum of money as compensation for the dismissal in return for being barred from pursuing that claim any further.
Acas has a great deal of experience in these kinds of cases, but its role is that of a neutral third party trying to arrange for the claim to be settled. Its job is not to advise you on the value of your claim, or on whether a settlement offer is good or bad, nor on the risks of continuing with your claim. If you are a union member, speak to your rep before accepting a settlement offer if you are in any doubt about it.