Hi,
Title of the product, I hope to explain well if you see the pictures you try to explain, sorry for my horrible English imm 01,02,03

As i am seeing in your screenshot.

You are using "Generic Child Product" custom field. When you choose an option from the drop down, the "Child Product" gets loaded and all the information from the child product will be shown. (title. description, picture etc..)

If the Child Product has a different product name than the Parent Product, then the Product Title will also be changed.
This is how "Generic Child Variant" works in Virtuemart Component. (it is a Virtuemart thing)

You can see the same thing in our Live DEMO:
demo.flexiblewebdesign.com/cleanmart/index.php/vm-product-details-page/product-details-default-layout

If you want to have "Same" product name, then you shouldn't use Generic Child Variant Custom Field.

Regards,
Support