Could my mobile phone network (in UK) be giving me a bad signal deliberately?

Sometimes I get a good signal, but there are many occasions when I don't. I have even stood next to someone who had a signal on my network (where I used to get a signal) but had no signal myself.

It did occur to me that my (inexpensive non-smart Samsung) phone could be on the way out, but then I went on holiday overseas and, on roaming, consistently had a far better signal than I get in the UK.

Could it be that as a long-standing contract customer I get low priority on available signal, or is that not possible?