movers, I need legal help with one

Hello, dear fellow members!

Perhaps someone has had a a bad experience with a moving company and was successful at getting his rights.  I would truly like to hear about it.

I paid my moving company in the beginning of May for the whole move from Canada to Uruguay.  The packing crew was very good.  Everything was put into storage in Canada as I did not know my final destination in Uruguay yet as I thought it would be better this way since they put things into the warehouse in any case until the container is ready, even if it is only a few days later.   (I have done this on another move and it worked very well with that mover.)

Neither this mover nor their Uruguayan counterpart did anything without being pushed repeatedly and continuously since then.  Everything that should have been done and was paid for, they did with much delay or not at all.

I nevertheless paid monthly the storage fees that I cause until the end of August, when I informed them that as far as I am concerned they can ship now.  Since then they have raised two more storage invoices (for September and October) although the further delay in shipping was caused by them. 

They now hold my shipment at ransom until I pay the September invoice (for now - October was not cancelled).  If I continue to feed them i am afraid that I will continue to pay and pay without things moving along and continue paying large sums of money especially during customs clearance, where the charges are much higher than for storage in a warehouse.

Thank you so much in advance. 

Armin