Getting help to review amount of refund paid

I am coming back to this forum, because it has been so helpful to me in the past. I live far away, so cannot call or exchange via post. During a visit in Europe, I posted my Self Assessment (Residence, remittance cannot be filled online) asking for a refund because an OT taxcode had been applied to proceeds from stock options, without taking personal allowance into account. I have already done this in the past and it was all OK (also thanks to previous exchanges with you). Much earlier than usual, I have now received a refund, but this is not at all the amount I had calculated and was expecting. I haven't received any explanation and cannot find any on the website. And the challenge I have is I cannot exchange with anyone because of my location. I believe there might be an error, so I would like to be able to exchange with someone from HMRC. I really don't know how to do that. Any guidance would be so helpful to me. Many thanks and thank you again for offering this forum.

Hi,
As we cannot look up your personal details on this forum, you will need to contact our Self Assessment team via the helpline or online using the link below to advise on your query.
Self Assessment: general enquiries
Thank you.

Hello, thank you very much for this, but the chat app doesn't work, as in, I am not going anywhere with it. So the only solution is a call, which I cannot currently do from here, at reasonable costs. But I saw others were posting quite detailed infos on specific situations, without sensitive data, so I just did the same as well in another post. Hopefully you will be able to revert to me on the second one. Thank you and have a good day.