Last October i canceled my Sonos music subscription service. Sonos did cancel the service but continues to bill me every single month. Despite multiple emails and phone conversations, Sonos support/sales cannot seem to figure out how they are billing me each month even though i give them my credit card #, email, name, etc. 

I can call my bank and chargeback all these charges but was hoping Sonos would actually research and resolve their billing issue which is occurring without my permission. Wondering if i need to have a lawyer send a letter to them?