According to Vi Rep:

If you recharge with a voice/data pack, the benefits will co-exist with your existing pack. If both the packs have outgoing & data service validity, the one with the higher outgoing & data service validity will be considered.

According to another rep:

If you’ve done more than one recharge, both recharges would be clubbed together. Benefits and validity will be extended to ensure you get the best value for your spend.

We hope this helps you. Still better confirm with Vi customer care if rules have changed or not.