Please tell me how to get rid of trapezius muscles.

I am an office worker who is concerned because whenever I look in the mirror or take photos, I can see that the line of my trapezius muscles running from my neck down to my shoulders is severely developed. Now that it has become visible, I am self-conscious every time I get dressed; even though it is summer, I cannot wear off-shoulder tops for fear of what others will say... I feel like I need to seek medical help before it is too late, so I have started looking into hospitals.

I've heard that body Botox is commonly used to refine body lines, but I would like to know how I should get the treatment for my trapezius muscles to achieve the highest level of satisfaction.

I am also curious about the level of pain when getting an injection, and which company's product is usually used the most.

Also, how many sessions would it take to get straight shoulders? Please let me know the cost as well!