Sadly all the records that concerned company designations were amongst thoes lost on the Battlefield at Isandlwana.
However a search of the Musters from 1874 - 79 may provide you with some very interesting details, and sometimes may provide clues at to what company the man served.
From the DNW Data Base:
Lot 570, 7 Dec 05
Category: SINGLE CAMPAIGN MEDALS
Hammer Price: £7000
South Africa 1877-79, 1 clasp, 1877-8-9 (536 Pte. E. Ivatts, 1/24th Foot) nearly extremely fine £4000-5000
Ernest Ivatts was killed in action at Isandhlwana on 22 January 1879. He enlisted at Abergavenny, Monmouthshire in December 1874, aged 18 years, and served in South Africa from the summer of 1875 until his death - ‘Effects recorded for claim by next of kin’ (The Noble 24th refers). [You must be registered and logged in to see this image.]
The medal to IVATTS