Angry client

Every single day I get more than 5-8 calls from different consultants telling me that the debit order that went off on the 20th Oct is not showing on their side . Debit order did go off. Why must I send proof that the debit order went off? Why can't they trace it on their side? I sent that proof to them on the 21st Oct already but till today I m being harassed. Someone needs to call me and explain to me how many more times am I gonna be harrased like this because I am so fed up now.