bad customer service

hi Woolworths firstly their quality is excellent but then they have flops as well long story short on Monday 20th November my app was loaded with a R400 voucher valid until 30th November. minimum spend R400 & I thought wow that's very nice & it said black Friday voucher. so on 23rd November I decided to go & buy some stuff knowing I have R400 free stuff but luckily b4 leaving home I decided to open my app & to my surprise the voucher disappeared & replaced by aR200 voucher same dates & minimum spend R200 hoz that possible so I called the call center & spoke 1 agent & then transferred to a another department & witch there ask so many questions b4 they can assist then say system slow to open your profile & then cuts the call my cell bill runs up for 17 + minutes & my voucher runs down by R200 if the voucher was loaded incorrectly whose fault is it. after sending emails no response but they tell you as a valued customer bla bla bla. please note you not a valued customer coz if you are a valued customer you cut the call or if the call got disconnected you will call back respond to emails & maybe take responsibility that it was a mistake by the person loading the app & we will give u the R400 voucher as it's not your fault that is *****ing from my app I took a screen shot of the vouchers so I got proof with date & times dont trust Woolworths & their app coz they can jimmy it anytime & furthermore Woolworths take all you'll vouchers and shove coz I'm not even using your R200 voucher that's a saving for you'll of another R200