Product: Debt collection

I 'm a member of the XXXX and have been activated on title XXXX orders for XXXX duty of various time lengths in the last couple of years. My civilian job has been very helpful and has worked well with me and my family with the transitions, up until this point, that is. The attached documentation is in chronological order and I will try to explain it in this letter in the same manner. 
The first letter I received was dated XXXX XXXX XXXX and it is telling me I have a debit of {$1700.00} in unpaid health insurance. I elected to pay for and maintain my civilian coverage while on XXXX XXXX to allow my family to keep our same providers and use my military insurance as secondary coverage. It states in the letter that my payments are scheduled to be taken out of my check and that I would maintain the pretax benefit with that. I elected to let that procedure take place as outlined in the letter. I was back at the XXXX from XXXX XXXX XXXX until XXXX XXXX XXXX ; I then went on XXXX XXXX for two more weeks from XXXX XXXX XXXX until XXXX XXXX XXXX. I then returned to the XXXX on XXXX XXXX XXXX and stayed there until I was activated on the orders that I am on now ; XXXX XXXX XXXX until XXXX XXXX XXXX. 
In XXXX XXXX I received the attached letter from the Treasury Dept. that stated I owed {$660.00} and listed a website and a telephone number. The website seemed suspect to me and was asking for all my personal information, so I called the phone number on the letter and left messages there, with no response. The letter also stated on the top my debit was {$660.00}, but at the bottom payment coupon it says I owe {$850.00}. I contacted my supervisor at the XXXX and he contacted XXXX of the XXXX personnel that are located in XXXX. They both advised me to wait until they checked it out to make sure it was legitimate. 
Next, I received a phone call on my cell phone from Pioneer Credit Recovery Inc. asking if I was XXXX XXXX, what was my birthdate, address and last XXXX of my SS. Of course I was very wary of answering, but then he told me my last XXXX! He wanted me to send them a copy of my orders and I told him the XXXX had copies of my orders and if they sent him to me, they can give him copies of my orders. This is what rekindled my efforts at finding out what is going on, so I contacted my XXXX Supervisor, and the XXXX person. XXXX sent me the information attached dated XXXX XXXX that outlined my medical insurance payments and what is still due. On page XXXX it states I owe a principle of {$630.00}, interest of {$2.00}, a penalty of {$6.00} and administrative costs of {$30.00}. After I obtained this information I mailed a {$500.00} check to the XXXX in XXXX XXXX with the attached XXXX XXXX XXXX letter. I have also attached an image of the cancelled check for {$500.00}. I will mail them the remaining amount when I find out if I am liable for the full amount. This brings me to XXXX of my questions ; Am I responsible for the interest of {$2.00}, a penalty of {$6.00} and administrative costs of {$30.00} or does the XXXX allow for these charges to be waived because they were incurred while I was on military duty and they are trying to be collected while I am again on military duty? I would also like this incident removed from my credit report. Does n't the XXXX XXXX XXXX XXXX prevent my credit from being damaged because of this?