Import problem with product variant

I am testing (Joomla 2.5) a new site where the import issue is fundamental and quite complex.
Each product has 3 packaging solution, and each has 3 prices (end user and two customer groups). I previously set: a)two groups at joomla "registered level" and b)a characteristic for package (confezione da:)
The test import csv file, for 1 product, is this:

product_code; product_parent_id;product_name;product_quantity;product_access;price_access;price_value;categories;confezione da:
xyz004;;Prodotto Prova 4;unlimited;;1;12;LEVAPUNTI ;1
xyz004_1;xyz004;Prodotto Prova 4;unlimited;;1;12;LEVAPUNTI ;1
xyz004_2;xyz004;Prodotto Prova 4;unlimited;;1;280;LEVAPUNTI ;30
xyz004_3;xyz004;Prodotto Prova 4;unlimited;;1;900;LEVAPUNTI ;100
xyz004;;Prodotto Prova 4;unlimited;;9;10;LEVAPUNTI ;1
xyz004_1;xyz004;Prodotto Prova 4;unlimited;;9;10;LEVAPUNTI ;1
xyz004_2;xyz004;Prodotto Prova 4;unlimited;;9;240;LEVAPUNTI ;30
xyz004_3;xyz004;Prodotto Prova 4;unlimited;;9;600;LEVAPUNTI ;100
xyz004;;Prodotto Prova 4;unlimited;;10;8;LEVAPUNTI ;1
xyz004_1;xyz004;Prodotto Prova 4;unlimited;;10;8;LEVAPUNTI ;1
xyz004_2;xyz004;Prodotto Prova 4;unlimited;;10;220;LEVAPUNTI ;30
xyz004_3;xyz004;Prodotto Prova 4;unlimited;;10;580;LEVAPUNTI ;100

The end user price is assigned as Access Level "Custom - Public" because setting all, when a user inside a group is logged in, two prices are displayed (end user and group price).
The problem is that, after the import, the product is declared "free" even if, in the administration the prices are correctly reported.
Changig manually the end user level in "all" and coming back, always manually, to the "Custom - Public", all is correct.
Looking at the administration nothing seems to be different immediately after the import and after the manual intervention.
Probably I didn't import some basic field, but I don't know which one.

I still have the problem. I tried to siplify progressively the cvs file untill the following:

product_code;product_name;product_quantity;price_access;price_value;categories
xyz0011;Prodotto Prova 11;unlimited;1;12;LEVAPUNTI

The problem persists: the product appears, in the front-end, as "free" even if, in the administration, the prices are correctly inserted.
I think that the problem is related to the "price_access" field. In fact, always, changing and restoring manually the selection of "price_access", in the backend, the problem disappears.

Solved !

The error was in the syntax of cvs, in the price_acces field. Each group must be declared with group id inside a couple of commas.
This is the correct csv:

product_code; product_parent_id;product_name;product_quantity;product_access;price_access;price_value;categories;confezione da:
xyz0015;;Prodotto Prova 15;unlimited;;,1,|,9,|,10,;12|10|8;LEVAPUNTI ;1
xyz0015_1;xyz0015;Prodotto Prova 15;unlimited;;,1,|,9,|,10,;12|10|8;LEVAPUNTI ;1
xyz0015_2;xyz0015;Prodotto Prova 15;unlimited;;,1,|,9,|,10,;280|240|220;LEVAPUNTI ;30
xyz0015_3;xyz0015;Prodotto Prova 15;unlimited;;,1,|,9,|,10,;900|600|580;LEVAPUNTI ;100

(I deduced this looking inside the table in the database)

Thanks for your always fast answers