what you have paid is a retention off set against taxes for capital gains liability.
In order to claim it back you have to process a declaration of renta (basically report your accounts/tax affairs to the hacienda)
I am not sure how often you can do this – I thought it was once a year.
It is unusual for the hacienda to give money back for the retention and I imagine they will be very suspicious of the fact you have sold for the same price – so you will have a real hard time convincing them
With regards to your solicitor. Have you tried speaking to them on the phone?
Did you pay them any money upfront?
It isn’t usually a solicitor who does this but a gestor (similar to an accountant) so unless your solicitor has a gestoria as well I am not sure why he would be getting involved in it.
<y advice would be to do the following
1. Send him an email and set Delivery and read receipt so you know it has been received
2. Write a letter to him asking him why he will not get in touch (there may be a genuine reason)
3. Call him and ask why he isn’t getting in touch with you
4. If all this fails send a Burofax (This is a legal fax that is recorded like recorded delivery)
5. If all else fails do you have friends locally who could go to his offices and see him?
As for the body to complain to it is the colegio de abogados but they are a real toothless tiger and do not do anything of use.
Hope this helps