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Set Value Labels to an Axis in Plotly (R)

Hello everyone,
I just need help with a simple issue. Please if you can help me I will appreciate it!
I am triying to plot a historical line with plotly in R, the y axis is numeric, buy I need that plotly understand that every simgle value wiill be interpretated like a letter.

This is how I do it with ggplot:

ggplot(historical,aes(Date,Rating,color=ID))+
geom_line(lty=1,lwd=1.15)+
geom_point(size=3)+
scale_y_continuous(breaks=brks,labels=labls)+
scale_x_date(labels=date_format("%Y-%b"))

brks= -1 -2 -3 -4 -5
labls= -1 -2 -3 -4 -5

and this is how it looks:

I need the same to this one:

So -1 -2 -3 -4 -5 will be interpretated as -1 -2 -3 -4 -5.

Thanks!!!

Correction
brks=-1 -2 -3 -4 -5
labls=“Aaa” “Aa1” Aa2" “Aa3” “A1”