Been calling 4 numbers for 6 days and NO ANSWER

I have a letter in the post saying I need to call 1 of 4 different numbers to query what actions need to be taken. The flowing 4 numbers ***/13/15/16. They are all engaged at different times meaning there is action happening at the other end. I have not been able to get through once for the past 6 days of consecutive calling NON STOP. My goods are probably already sent back and there is nothing I can do because the phones just DO NOT EVER get answered. I know our customs department are USELESS but this is unheard of. Atrocious behaviour. Someone needs to fire that whole department if they cannot pick up the phone, it doesn't require a degree, come on. As I type this I am going through the different numbers all engaged at different times yet NO ANSWER. Shocking and pathetic