Toyota Corolla XLi official service intervals

I recently purchased a Toyota Corolla XLi Petrol in Lahore from one of the main dealers. We was told to take the car in for a 1000 KMs check/service. We took the car and the guys there simply checked and said its ok. At the same time the supervisor in the workshop told us that the next service is due after 10,000 KMs.
Now the car has done about 4000 KMs. Just to clarify, it is still on petrol. (not on CNG as yet because we wanted to drive it without CNG for a bit in case we see any early manufacturing faults with it). My brother went in to get something else the other day, and they informed us that we should have had it serviced (oil change) every 2500KMs !!! and a filter and oil change every 5000KMs !!!
They also claimed that they havent asked us to come back after 10,000KMs and also asked us who exactly told us. My brother simply told them, that we do not keep a record of who speaks to us in their shop, and did not record the coversation
Any how, we had the car serviced which came to quite a lot of money. I am not in Pakistan currently so couldnt argue with the guy..so...

My two questions are below is

How often does the service have to be done according to your car dealer?

How ofter does the service have to be done according to the service/warranty book?

I ask because changing oil every 2500Kms is absolutely crazy as it is only 1526 in Miles. I have only heard of cars needing an oil change at 8,000 MILES or more. I already understand the reasons that there is a lot of dust etc in Pakistan and that the oil is not good quality etc, but the difference in 1500Miles and 8,000 miles is HUGE!!

Please help answer my two questions above according to your experience and info.

Thanks,
GB.