Poor Service

So today I went to the Branch I bought my Suzuki Ciaz 2019 Model from just to ask when is my next service because my service light didn't come on. First salesman were not sure if there were a service light. No stickers that indicate when next service is due. We went to the service Department the Lady said clients Complaint because of the fact that there are no indication. Long story short I purchased my vehicle on 37000km. Vehicle Last service was done on 26318km. The day I Purchased the vehicle Salesman said car was serviced so 10000km from that is 47000km or as I know 45000km for a major service. The branch said my warranty has been voided. So today I just want to say train your staff to give the correct information to Customers and indicate to them with a small piece of paper when the vehicle is due for a service like rental companies.