VODACOM 4U CAPE GATE GIVING ME HARD TIMES

I bought my phone at vodacom 4U Cape gate. X7b honor phone on the 9June 2024. I only used the phone for less than 7 days. I decided to take back as it was still under 7 days. The phone was having echo sound when someone receives my call that was my problem with. They took the phone back and promised me to exchange it. I thought it will be quick. Am going up to 2 weeks now without any response. I went there several times asking they always telling me stories of courtier and accesor please help me. Tht phone costed me a lot