Qatar Airways — Failing to Notify Customer

Dear Qatar Airways,

I'd like to file a complaint since I had bought the flight ticket but I was being denied boarding. It was said that my ticket was invalid.

I bought the ticket in advance on April 18, 2022 - a return ticket Stockholm - Jakarta, Jakarta - Stockholm. I got an email confirmation along with the e-ticket. It was written that the booking status was confirmed.

My flight to Jakarta was scheduled on July 15, 2022. However, I suddenly had a business to attend in Japan on July 14, 2022. I tried to call Qatar Airways team to modify my flight to Stockholm - Tokyo, Jakarta - Stockholm. However, I was told that the flight modification was not possible. Thus, I bought another single ticket Stockholm - Tokyo, without cancelling the return ticket Stockholm - Jakarta, Jakarta - Stockholm.

I didn't check-in for my flight Stockholm - Jakarta, since I was not there and I wanted to avoid 'No Show' passenger. Little did I know that my ticket became invalid because I didn't check-in. I am a frequent flyer due to my job and that was supposed to be my first time flying with Qatar. However, I was left disappointed due to some points below:
1. I was not notified that failing to check-in for in-bound flight entailed to the cancellation of the ticket.
2. It was difficult to contact reservation team and/or customer service when the problem arised. There were numbers given to me by Qatar Airways team at Soekarno Hatta International Airport, Jakarta. One of the numbers could only be contacted with Indonesian number, while I have a Swedish number. Another number couldn't be connected. I couldn't get help with Qatar mobile app as well.

I'm unhappy about this poor service. I had paid the business to do a service but it hadn't been done. I'd like to claim for compensation.