No they can not take money out of a 401k, but they can stop making contributions and still deduct money from your paycheck. This happened to people who worked at a company I previously worked for. Fortunately it was a few years after I left and had received all of my contributions. Unfortunately the Boss (owner) was a good friend to all of us. This tore a lot of friends apart. The boss died before any charges against him were filed. The company filed for bankruptcy and my friends received only pennies on the dollar and it took several years to recover that.
You should be receiving a statement from the independent company directly, not from your company. Check to make sure that the amount that is deducted from your check is being deposited into the independent account.