ISP Telling Me I Have to Sign New 3-Year Contract In Order To Increase Bandwidth

I am currently about 17 months into a 3-year contract with a regional ISP that services 5 of our locations with dedicated Internet access over fiber. 4 out of our 5 current locations are not directly in our ISPs fiber footprint thus requiring us to have 3rd party last mile providers at these locations. One of the locations has Spectrum, one has AT&T and the other two have local carriers who also own a stake in our ISP (i.e. our ISP is owned by many local carriers and these two locations utilize these carriers for last mile services). Our current services are all 10x10 with the exception of the Spectrum office which is 5x5 (don't judge, I know these are all sad). We don't have any services beyond dedicated Internet and some SIP trunks. No MPLS or other VPN technologies, nothing complicated.

Our company recently purchased property to build a new branch and I have started getting quotes for the telecom services. I first called up our current ISP and got a quote but, upon taking it over to /r/sysadmin's Am I Getting F**ked Friday I realized that the pricing was outrageous so I found a broker and started looking at other pricing. In the meantime, I realized that the price per megabit we pay in our other offices is now extremely overpriced (it wasn't when we first signed up) so, I went to our current ISP asking for quotes to upgrade stating that I felt like we could get more bandwidth without raising our bill too much as it appeared pricing within the industry had come down. Well, my Account Manager shot back at me and has now firmly stood her ground on the claim that we can't make any upgrades without signing a new 3-year contract because they would have to sign a new contract with the last mile providers. This all sounded very fishy to me. I could understand requiring a new 3-year if they were going to have to build-out more infrastructure but to simply add 10mbps to an existing installation and the overall bandwidth remain under 100mbps, it seems absurd to require a new contract.

I briefly ran this by the broker I am working with for the new office and he said it sounded like she was just trying to make year-end quotas. I really wanted to see what y'all thought about this claim, is it common or is it just a sales tactic to pressure me into signing another contract?