If you were sued and properly served with the Complaint and Summons, you should respond to the complaint in writing; a phone call to the opposing party or attorney is futile. It is best that you hire an attorney to help you with crafting the right response. You would not do surgery on yourself by watching a how-to video on the internet, so copying and pasting something from the internet is not advisable. You may be able to file a Motion to Dismiss or have to file an Answer; an attorney who handles lawsuits will be able to properly advice you.
The attorney will need to know specific information about your case when drafting the Answer and may also be able to raise defenses to the lawsuit. You can help yourself by gathering all of the information related to your case, e.g., emails, contracts, pictures, letters, notes, etc. Making a timeline of what happened is also very helpful for you and your attorney. It will also save you time by not having to repeat information, you won't forget when events happened if you take the time to write them down and, at the same time, will keep your costs low.
Not timely answering the lawsuit is fatal. You essentially gave up all your rights to defend yourself and try to resolve the matter. Once a default judgment is entered against you for not responding to the Complaint, the plaintiff (party suing you) has a strong upper hand and can request from you a lot of financial information in order to recover the amount it was awarded by the court. Many cases can be resolved but you must take action to avoid dire consequences. Consult an attorney right away after you are sued.