D-LINK MODEM WORST PURCHASE

The D-Link modem was the worst purchase I have ever made in my life. Struggled with setting up device at home - was then told to go into store to set up. Technician was able to assist with setup - but then left his sim card in my phone because mine didnt fit at the time. I then had to take time off work to go to Telkom to do a sim swop - Or loose the 20GB that was left on my sim. After that - the modem worked fine all day, we even had 2 devices linked to it - worked well This morning - device was not reading the sim card this same sim card - not able to connect to my work laptop. After this - device keeps switching off - and it is charged. I have to make sure of that because I'm using this device for work purposes. Do I have to waste more money going to buy a n ew modem at a different store. This is a complete nightmare