Groups who use the hall in Llanwinio said they would hand in their keys after the rent tripled and they were asked to sign up to a 25-year lease.
Peter Walton, from the association that runs the hall, described the changes as "unreasonable and unfair".
But the Diocese of St Davids said as a charity it was "obliged by law" to charge market-value rent.
Rent costs charged to the Community Association of Volunteers are set to increase from £250 to £750 a year and it will also have to meet the costs of the insurance for the first time.
The St Davids Diocesan Board of Finance (DBF) said: "A proper valuation of [the rental value] was undertaken and the rental charge increased in line with that.
"The rental goes to the parish, not the DBF, hence keeping it within the local community."
But Mr Walton from the Community Association of Volunteers told Newyddion 9 the finance board was behaving in an "unfair, unreasonable and unjust manner".
He added: "It's not just the money... we will be taking all of our belongings out of this building on Saturday 27 February and we'll be handing the keys back unless there's a change of heart."
A row has broken out between community groups and a Carmarthenshire diocese over the cost of using a church hall.