Bad Service

I bought Lenovo machines from Tarsus on 8 March 2021 and one of them had a problem with the screen. The machine switches on but the screen doesn't power on it remains blank. I called Lenovo and was advised to take the machine to Partserve for a credit note as this was within 8 days and is covered by the warranty policy. I booked the laptop at Partserve and was told I can't get a credit note the machine needs to be assessed. I left the machine for assessment and 3-4 days later I was told it's fixed I can collect. I collect the machine and send it back to my client only to experience the same problem.

I went to Partserve again and was told the machine needs to be assessed again, when I enquired about a credit note I was told that it is not possible as the approval needs to come from Lenovo after assessing the machine. I called Lenovo and explained my situation and that this machine was previously assessed but still have the same problem, their response was only Partserve could give approval for a new machine. The question is who do I believe, who is responsible for assisting me here? The sad part is the people I purchased from Tarsus, are not involved, I do the running around and my client's business has to be compromised because no one wants to replace the faulty machine. Our business as SMEs is compromised by these big companies not giving us the service that is deserved. According to their warranty policy, I am supposed to get a new machine instead of running around with multiple trips to Partserve. What about the other cost I keep incurring with all these trips?? I feel that the 3 companies (Tarsus/Lenovo/Partserve) involved are not being fair to their client.