You may have seen that almost every tone option is exploited in this conversation. Both speakers, for example, use the rising, a tone said to express dominance or some kind of power (Brazil, 1997). In addition, you may have noticed that each speaker has a specific function: Kurtis, probably, being a customer service agent and Salena, a dissatisfied customer. Who do you think is powerful? Do you think power remains constant in a conversation?
In the passage OK, let me just pull up your account. Just a moment, the speaker has the power to conduct the conversation following a procedure (normally scripted, for instance, for call centers), and so he controls communication at this stage, telling the hearer that she has to wait until he accesses her account and does what needs to be done. In this light, we can make sense of this use of this so-called dominant tone.
At a certain moment, the customer says I've been down that road. A few times in fact. Apart from being shared information at this stage (hence the use of the referring tone), these tone units represent Salena's complaint to the company for a service that hasn't probably been rendered properly. It can be said that she adopts a powerful position at this time, questioning the information passed by Kurtis and stating that she shouldn't be experiencing what she actually is.
This little analysis goes to say that we can't say a priori that in a two-party conversation like the one above, one speaker (for whatever reason) will systematically be powerful and the other, powerless. As much as everything in life, oral communication is more dynamic and sometimes unpredictable, with power possibly being fought for by any speaker at any stage.
Reference
Brazil, D. (1997). The communicative value of intonation in English. Cambridge: Cambridge University Press.