Pronunciations: differences between spoken word on its own v. in a sentence

Why is a word often pronounced differently on its own versus when it’s in a sentence. In one of the Absolute Beginners courses (for Spanish) the word ‘llamo’ is pronounced with a hard j compared to with a soft i when used in a sentence. This is confusing and it’s not the only example. Thank you!

Is it the same speaker both times?

If so, it probably has something to do with connected speech. When you speak a sentence naturally not all sounds are pronounced like they would be when you say the word in isolation (or a deliberately trying to articulate it), we do it all the time in English i.e. ‘I’m going to the shop’. Spoken naturally, the final g sound disappears or 'I’ve been sleeping - been the sound actually more resembles ‘bin’ than it does ee.

If it is two different speakers, then it is highly likely that it has something to with accents. Spanish has a huge range of accents and the “ll” sound is one that I’ve noticed can vary quite a bit from region to region.

I hope this helps!

p.s. I’m pretty sure my second reason is more correct in this case