Initiated contact via written notification of billing errors on XXXX XXXX 2015. Citibank failed to acknowledge and to respond to our Fair Credit Billing act dispute letter. Certified letter was recieved by Citibank of XXXX XXXX, confirmed via recorded telephone line. Contacted citibank multiple times and failed to return call after asking to investigate verbally as well. Last correspondence was via phone on XX/XX/2015 and citibank account manager refused to investigate, escalate, or resolve issue. 
