Bad service at Telkom

I went into Telkom Century City on the 8 May to sign up for the 40g Huawei B315 package 20g day AND 20g night where I found out modem was faulty, the 11th May I took back the modem for repairs and only received it back on the 2 June which I had my sim in my wallet since I gave it back so I did not use any gigs. This is almost a month which I did not use it and I did not know that the data falls away as per emails I received by Elvis. As far as I know the data is carried over cause the lady(Savanah) in the store said so.

They are not responding to my mails so I need something to be done as this is unfair to me as the customer as the fault was on their side and I had to go in and fetch the modem they did not even call me when it was ready to collect and now I must be inconvenienced.

Why should I pay for 2 month subscription data and only use up 1 month that so wrong.