Hi,
I think it´s late to reply but it hurts to hear you say that.
I´m a spanish "Arquitecto Técnico" of Murcia( There´s no equal profession in your country) but you will know about us because to make your new house it,s compulsory to contract one as you contract an arquitect.
Of course you can change your arquitect when you want. You only have to dismiss him. You have payed him for two concepts:
1)A project you must have in your hands that make you to obtein a license in the townhall for make the house
2) "Direccion de obra": The way he manages the constructor to become his project a reality. When construction is finished you need a certificate signed for the arquitect and the "arquitecto técnico" to obtein the license of first ocupation.
Any time during this work you can change the arquitect.
For example:
If the building is at 40 % of construction level in the moment of the dismission: The first one must certificates the construction for this 40% and the second one will be responsed of the rest .
If the first arquitect take you in troubles, the second should speak with him to solve thems
I have been in this situation for two times and without troubles.
Remember that you pay and you are in charge in your house.
Sorry about the extension of the reply and for my poor English. I only trying to help.