what do you mean by contacted asda?
please don't get me wrong but if it is in the premise or on their wall [which most are] they are duty bound to give you an address to write too.
did you visit the store or use asda HQ website?
Don't touch them owe me £500 since January 2019 make excuse after excuse. Seem they always have software problems sending money out. Keep saying they will call back or email nothing been chasing it now for 6 mths the phone staff always have the same banter we will chase it up and get back to you then nothing!