Continue Harassment

Continuous harassment. I have not agreed to, or signed any agreement with them, therefore I am not liable for any amount that is being charged which is their fees. The agreement is with the orthodontist and themselves. My account was in the current said days as stated on the invoice/statement which was paid during that time, however it is not my fault the orthodontist in question sold his practise and the terms immediately changed. Therefore after numerous emails to Credit Intel, they bluntly ignore this, and continue to harass.