Monitor issue, worst customer service experience, unresolved after 45 days

Based on the recommendatioon from the technical support of Dell through chat, I purchased two minitors and a dock station! First of all, the dock station was not compatible with my laptop although I gave the information to the tech team. More importantly, one of the monitors has been malfunctioning from day 1 and has some horizontal black lines in it. When discussed with the customer care, they told us that they are going to mail us a new monitor and we can return the malfunctioning monitor in that package! It's been almost 50 days and we contacted them multiple times. Emailed them all the images and details they asked for but we have not got any updates yet. It is our worst purchasing experience ever. We are super unhappy! We need the issue to be resolved asap after almost 2 month!