Unable to work due to Hostage situation with ISP

I've been in contact with them and was promised I would easily be able to switch and upgrade my speeds once my voucher expires, the time came and for a whole week nobody responded or helped. My calls were dropped after wasting so much airtime trying to get through and when I now eventually get through, I'm being told I cannot have my line speeds upgraded until 1 October which is not what I was told I initially. Because of this I am now in a position where I need this upgrade for work and am being held hostage by this ISP. Ridiculous!