Sqeeling Serpentine belt AFTER the repair

Recently I had my serpentine belt and the pullies replaced. I am not sure that work needed to be done. After that, the belt squeeled. I returned my car to the shop where the said the the the belt tension needed to be replaced. I went ahead and had the work done, since I was really over a barrel, but I suspect if the tension was bad it was due to the replacement of the pullies not normal wear and tear. Do you think the tension became a problem due to bad job with the pullies?

No. But I’m confused.

The year, make, model, and mileage of the car always helps. However, I don’t know what you mean by having the “pullies [sic]” replaced.

The pulleys driven by the serpentine belt are on the harmonic balancer, the alternator, the AC compressor, perhaps the fan clutch (depending on the vehicle), perhaps the water pump (depending on the vehicle), perhaps a smog pump (like on my old '89 Toyota Pickup), and the tensioner, and perhaps an idler pulley. I doubt that you had those that are driven by your particular belt all replaced. Exactly what was actually done? And why are you “not sure that the work needed to be done”? Explain please.