If this is software post-sales support, I don't fully understand.
Even in the UK, many of IBM's software products no longer have an in-country post-sales support operation (there was rumored to be a deal where each platform's technical support was aligned to just one european country. The UK only got x86 and related software packages which were immediately sold to Lenovo).
So for AIX, TSM, GPFS and a lot of other AIX specific products, you will almost certainly end up talking to someone from another country (often outside of Europe, even) for the whole duration of the problem, and trying to get someone on-site for a software problem has been almost unheard of for at least a decade! Any on-site visit for software has been regarded as paid consultancy, not post-sales support.
It was when I was getting TWS/LoadLeveler support from China (who at the time were supposed to be off the list of countries that products could be procured from) for a UK government organization that I started getting really worried.