How to change sort by icons "+/-"

[VMRESLO]

Hello everyone!

Can anyone please tell me how to change the sort by icons "+/-" to "uparrow/downarrow" or even words for example "ascending/descending"? I would like to have the sort by for example "Ordering ascending/descending" and not "Ordering +/-".

I am using VirtueMart 3.0.6.2 on joomla 3.4.1.

Thank you and best regards to all!