Well, as to the lying, that's DH's job to address.  He should sit her down and let her know he figured out she has another phone, and let her know that he understands that she feels pressure to lie, but that's it's not OK, and she doesn't have to lie just because BM asked her to.

As for Napoleon, ignore him. Flat out ignore, no response.

SD11 needs to know that lying is not ok, and this is a great example! DH needs to communicate with her - consider it a teaching moment.

Ignore Napoleon. How dare he issue edicts to you - only the bio parents can do that, he has no say so at all. He is the step-aside.

If she has a second phone, cut off the first one.  No sense in paying for two, right?

As for Napoleon, put that tiny dancer on ignore.  

I really feel for the child in this case. As you pointed out she will lie because she was told to.

I honestly don’t know how I would approach it. You can’t do anything about BM giving the child a phone and preventing you guys from contacting her through it as long as she maintains another way for you to communicate with the child.

You could cut off the phone you gave her if you feel it’s not being used. MAYBE BM would “allow” you to contact the girl through the new phone or else she would have to make her accessible some other way.

Honestly I would worry about the phone you gave her since it’s the only thing you can control. As long as she continues to follow your rules that’s the best you can do.

We had a similar situation, Meth Mouth went out and got SD a new phone and plan after we shut SD's phone down to nothing since she was sending and uploading naked photos.

We just shut off the phone line we had for her and DH asked for her new number, but SD was also 17 at the time.

DH should talk to SD and let her know that since she now has this new phone he would like to shut off her old one, and could he please have her new number so he can keep in touch with her.

As for Douche Canoe he can kick rocks, just be prepared they might just block you on her account regardless.

My SSs have been taught to lie to get what they want. It drives me crazy, but I won't change their behavior, because BM uses the same tactic. She actively tells them to keep secrets from DH and then tells them lies that she passes off as "secrets" about DH. One example, SS said, "Dad, I know secrets about you, mom told me how you caused the divorce." Um, ok, too bad BM filed for divorce after she met her current SO. Also, too bad the truth is that DH and BM never should have gotten married in the first place, so the thing that really caused the divorce was their getting married. DH wanted to be married because MIL told him at his age (25 at the time he got engaged)), he should be married. BM probably thought DH was the only person who would ever agree to marry her. How she managed to find anyone else is beyond me...but I think her current SO is a con artist who is taking advantage of her, so that might be why. 

Ugh, I am in the same position right now! Crazy dropped lunch off (Lunchables...) for skids a few weeks ago, 2 days in a row. They have plenty of food at our house to bring for lunch, with healthy options, and she brings them crap. Both days, SS12 lied to me about it. The first day he told me he didn't eat the leftovers he was supposed to have for lunch because he "forgot them, and just ate a little lunch". The next day as he was walking out the door without a lunch, I asked him about it and he said, he forgot to pack one, and then ran and grabbed a few random things (like a fruit cup and granola bar), and said that would be enough food for him. Well he knew that Crazy was bringing him lunch, but he lied. I mentioned it to my SO, and he said he wasn't going to say anything to him because he wasn't going to put him in the position of feeling like he needs to choose a side. I get his point, but then all lying is excused when it comes to Crazy? I think that is setting a terrible precedent. This isn't the first time it has happened, either.

I'm not sure what the answer is, but I don't like excusing lying.

The more they lie (especially without consequence) the easier it becomes.  I think what Tog Redux suggested is a good approach for your husband to take.  He should definitely address it.

Look the kid in the eye and inform them that people who lie are just pieces of sh*t.  And if they choose to be liars then they will never be decent human beings.