Failing to assist with activation

I have received my device with 2days after completing my application which is great. The communication from when I started my application till when I received it was also great. However I am struggling to activate my device and I have trying to get hold of Rentoza on all their channels and I have not received any response from Rentoza. I even tried calling but their number goes straight to voicemail. I am so disappointed. I can't express how I fell at this current moment