Info on Lakota Cash

My boyfriend took out a loan with Lakota Cash in South Dakota. We had a bad issue where i lost my job and was not able to pay them when required. we offered 2 do minimal payments and they declined. We asked could they send up a payment note. Of course, they refused! Now that i have graduated from school and on my feet to help my boyfriend, they have been leaving harassing calls on his phone and at his job threatening to issue a warrant for his arrest. His job is threatening to fire him if he doesn't control the calls. We have even asked for a 2nd time to send out a bill or payment note to make sure it is not a scheme. Again, they refused to do so!!!! So what info can be useful ? Thanks!