No Signal while in office building

Good day,<br> <br> I have been with Cell C for almost 2 years. My cellphone contract expires in exactly 1 month. I have another data contract as well.<br> <br> I work in the Centurion area but when I enter our offices for work, I receive no signal at all. I receive no phone calls, I can't use any app which requires data. In 2014 I used to roam on to vodacom and now my sim card says this is unavailable.<br> <br> This means for at least 8-10 hours everyday I have no signal. I logged a previous complaint before while studying at the University of Pretoria as this no signal issue was occurring as well while in buildings. Cell C said they were upgrading their infrastructure.<br> <br> Is there a way around this? Why can I not roam on vodacom during the day anymore?<br> <br> Or should I just take out a contract with another network so I can have signal during work hours?<br> <br> Please advise? <br> <br> Thank you:)