Qatar Airways complaint: Missing refund

Yesterday was the 10th of September.
5 months ago I started an air trip booked with Qatarairways.
5 months ago I asked Qatarairways for help at the airport of Manila, Doha and Dar-es-Salaam, because the first flight had been amateurishly booked wrong. The subsequent flight would have been in the air for 1 hour already. In addition to the complications at the airport, there would have been an overnight hotel stay and another PCR test.
So for 5 months I have been in contact with Qatarairways.

Success: none!!!
Good service: definitely not!!! There is not one serious answer.

I still insist on the payment of 300 USD, because also the last flight had been booked totally wrong: the following flight was the day before.

I did not use the flights from Dar-es-Salaam to Doha and from Doha to Manila.

The whole ticket was 1786.40$
All canceled return flights should be half of the price
Half of 1786.40$ is 893.20$
Refund by Qatarairways 690$
Difference: 203$
Missing refund of PR1818 100$ (estimated)
A total of 300$ is missing as a refund!