You must contact the court, probably the court coordinator, but maybe clerk. They might have you talk to Probation Officer. Many of the courts have their own forms to do this, so you won't need anything prepared in those courts. Some courts require that you bring in a formal request for removal and documentation from Smart Start about no violations, so these are questions for the court staff. Try talking to them by phone first. If you want to make it easy, contact an experienced DWI attorney to help you.
Smart Start is correct - you must have a court order to get the device removed since it was put on with a court order. Talk with your probation officer first and be positive that it is not a condition of probation, then ask the p.o. if they can help you. If not, then I would call the court coordinator and explain the situation and ask if you can have an appointment with the judge. What will likely happen is that the coordinator will confirm your infirmation, talk with the judge, and the judge will simply sign an order. The coordinator will call you to pick up the order to present to Smart Start.
If this does not work, call your original lawyer and see if they will run by and ask for the removal. It should not be a big deal except for confirming that in fact you do not need it for your probation. Your terms of probation will be in the clerk's file and should not be that hard for the court to retrieve (rather than having to get your original file from your p.o.)
That was a smart move on your part to keep the device but it is costly. I hope it helped with your kids.