UK Visitor Visa for Parents - Change of Dates

[srihariramani]

Hi,

I currently hold UK Tier 2 ICT visa.

My Parents received UK visitor visa stamped. They applied together from VFS Chennai on 20-Apr-16 but their visa start date/duration is different. Mom got a visa start date as 26-Apr-16, while dad got correct start date 26-May-16 (Actual travel date).
Is it possible to change mother's visa start date?
If Yes, please let us know the procedure and timeline to get the dates changed (only for Mom's visa).

Have raised the same query in UK immigration website (https://ukvi-international.faq-help.com/#) but no reply.
Any advice would be highly appreciated.

Thanks
Sri