Amplifier Repair not on time promised

On 4 May 2025 I took my amplifier for repairs they said it will be back in 20-25 working days which has past already, I have no problem with waiting my issue is that I have to use it next week Saturday on 14 June without that amplifier my life is ruined and I haven't received any calls from them when I call them they say they don't and drop the phone. What do I do regarding this matter? I'm referring to Cash Crusaders Amanzimtoti. More over I read some reviews, other people have experienced such matter. Please some help