@futuroexpat I thought about that. In fact, I have made a request that they cancel the old contract and give me a BRAND NEW, ONE-YEAR contract at the new (higher) rent, and... no response.
This management seems quite unresponsive and inflexible, so it wouldn't be so bad if I decided to pack up and go live elsewhere when my lease ends in December. I'm sure I'll have to pay a higher rent at a different place (I got this apartment on a discount), but I should be OK... especially since I'll be looking for an UNfurnished place... I got this current place unfurnished so I had to buy all my own stuff anyway, including the dang curtains believe it or not.
Back to your point... I have never heard of a situation where the renter can refuse to pay the higher rent. I mean, the rent increases are spelled out in the Contract, actually... it follow some Colombian standard about rent increases following Inflation, etc., which I have heard from other people before (here in Barranquilla, and when I went property-hunting in Cali), even before this apartment raised the rent on me.