Oman Air review: wrong information and unnecessary charging

Oman Air,
IGI Airport, New Delhi
On 1st January 2020
Dear Sir/ Ma'am
Compensation claim for wrong information and unnecessary charging
I am writing regarding flight WY-0242 & WI-105 on 1st January 2020 from IGI Airport Terminal 3 to Manchester Airport via Muscat with the scheduled departure time of 10:20am. My booking reference is TINVGI.
Prior to taking this flight, I checked with your call centre on three occasions regarding carrying of a large frame. I was advised on all three occasions that there will be no additional charge and I can carry the item on flight with me.
However, at the airport, I was charged INR 12, 747. I find this utterly unacceptable. If I had been given proper advice, I would not have carried the item with me and incurred the charge. I am so disappointed with how I have been treated.
I am seeking a refund of the amount that I have paid.
I look forward to hearing soon and I can be reached at below details
Yours sincerely,
Kuldeep
[protected]@gmail.com