How do I register a complaint?

I bought. a laptop in March.  After one month it stopped working. Still under guarrantee and having paid extra for premium support repair or replacement I contacted Dell. Technician called and did a partial repair. He provided a service report which states problem not resolved, he phoned someone whilst in my house to request a part and said he would have to come back. Waited for 6 weeks, numerous WhatsApp messages thanking me for my patience.

 Well my patience has run out. After this length of time I requested a replacement laptop I provided all the information on WhatsApp service number contact details service report etc etc. Then I was asked to write this on a piece of paper and photograph it with the laptop and send photo within 24 hours. Despite them having all the information already and thanking me for my patience they asked me to do this within 24 hours!! Well I did it took about 72 hours because laptop was my daughters 21st birthday present and in her possession. Then I received an email saying a technician would call the next afternoon. I waited in. Then another email saying technician rescheduled to next day. Then voicemail saying the part had not been delivered to them and that I won’t hear from them until further notice. So now asked on WhatsApp when will I receive the replacement laptop, and just have message will update me as soon as possible. 
  Who knows how long that will take another 6 weeks?
   When you pay for support you expect to get it.
    I get the impression that Dell departments don’t speak to each other.

   It is a problem with their product and they are making me suffer for it with all this runaround and stalling and requesting the same information numerous times.

   I want to complain. And I want a replacement laptop. It’s only worked for one month out of the 4 that we’ve had it.

 I feel like screenshotting the ridiculous WhatsApp chat for social media.