Self Assessment refund and contacting HMRC

I requested a refund on my Self Assessment and according to the online 'when should I expect a response' form, I should have had a response weeks ago. I have as yet had no response, the credit is still showing on my account, despite bank details submitted with the Self Assessment forms and also within the 'request a refund' form online? I decided to try and call about this, but I can't get through on the telephone. I have tried on a number of occasions over the last 3 weeks, answering the security questions and relevant department requests etc, but I keep getting a message that just says that no one is available, sorry for the inconvenience, then get cut off.

Hi,
I'm sorry for the issues you've experienced in trying to progress your repayment claim.
If you haven't received it 10 working days after claiming, it's most likely that your repayment is undergoing some additional
security checks - these can take up to 6 weeks to process.
To allow us to check on the progress of your repayment, contact us by webchat via Self Assessment: general enquiries
Thank you.

I have had the same issue, get cut off immediately after answering all the security questions – several attempts!