WBTT(TRC20) is a wrapped BTTOLD(TRC10) token. It is pegged 1:1 to BTTOLD.
To exchange WBTT for BTTOLD, please visit: https://just.tronscan.io/#/wbtt
To exchange WBTT and BTT (TRC20), please visit: https://sunswap.com/#/v2
To exchange WBTT and TRX, please visit: https://sunswap.com/#/v2
To exchange BTTOLD for BTT, please visit: https://wallet.bt.io/swap?language=EN
To exchange BTT for BTTOLD, first exchange BTT for WBTT, and then exchange WBTT for BTTOLD. At this time, there is direct way to get BTTOLD.