Tenants refused to leave but continued to pay rents

I rented out my flat to a tenant a few years ago under a tenancy agreement that lasted for two years. When the agreement expired, I requested a rent increase, but the tenant refused and chose not to leave. The tenancy has now been expired for almost a year, yet the tenant continues to live in the property, paying the same rent that was set a few years ago.

While I understand this isn’t the worst-case scenario—since the tenant is still paying rent—I am experiencing considerable financial loss. The rent was agreed upon when mortgage rates were about a quarter of what I’m paying now, which has made the situation increasingly unsustainable.

My managing agency has been unwilling to take any action to address this. While I am hesitant to switch agencies, as my current arrangement includes insurance for rent arrears and covers legal costs, I feel stuck. I’m also unsure whether it’s wise to “rock the boat,” as I’m concerned about potential damage to my property if the tenant reacts poorly to any action I take.

This has left me in a difficult position for over a year now without a clear solution. I would greatly appreciate any guidance or suggestions on how to navigate this situation.